WO2021055599A1 - Methods of hole injection in indium aluminum gallium nitride light-emitting diodes - Google Patents

Methods of hole injection in indium aluminum gallium nitride light-emitting diodes Download PDF

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WO2021055599A1
WO2021055599A1 PCT/US2020/051264 US2020051264W WO2021055599A1 WO 2021055599 A1 WO2021055599 A1 WO 2021055599A1 US 2020051264 W US2020051264 W US 2020051264W WO 2021055599 A1 WO2021055599 A1 WO 2021055599A1
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layer
active region
iii
gan
type
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James S. Speck
Morteza MONAVARIAN
Claude C.A. Weisbuch
Cheyenne LYNSKY
Guillaume LHEUREUX
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The Regents Of The University Of California
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30604Chemical etching
    • H01L21/30612Etching of AIIIBV compounds
    • H01L21/30617Anisotropic liquid etching
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30604Chemical etching
    • H01L21/30612Etching of AIIIBV compounds
    • H01L21/30621Vapour phase etching
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10HINORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80Constructional details
    • H10H20/81Bodies
    • H10H20/811Bodies having quantum effect structures or superlattices, e.g. tunnel junctions
    • H10H20/812Bodies having quantum effect structures or superlattices, e.g. tunnel junctions within the light-emitting regions, e.g. having quantum confinement structures
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10HINORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80Constructional details
    • H10H20/81Bodies
    • H10H20/819Bodies characterised by their shape, e.g. curved or truncated substrates
    • H10H20/821Bodies characterised by their shape, e.g. curved or truncated substrates of the light-emitting regions, e.g. non-planar junctions
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10HINORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
    • H10H20/00Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
    • H10H20/80Constructional details
    • H10H20/81Bodies
    • H10H20/8215Bodies characterised by crystalline imperfections, e.g. dislocations; characterised by the distribution of dopants, e.g. delta-doping

Definitions

  • a light-emitting diode or laser including intentional V- defects and a planar hole waveguide is disclosed.
  • the active region includes a quantum well (QW) on or adjacent to a quantum barrier (QB).
  • the planar hole waveguide comprises a barrier including (i) an Aluminum Gallium Nitride (AlGaN) interlayer in the QB or (ii) a delta doped layer at the interface between the QB and the QW to enhance holes lateral diffusion length within the QBs prior to being captured by the QWs, which ensures or increases volumetric injection of holes into the active region.
  • AlGaN Aluminum Gallium Nitride
  • the present disclosure describes designs and geometries such as rectangular, pyramidal and triangular-ridge injectors to engineer the hole injection homogeneity and the efficiency droop in LEDs with different emission colors.
  • the designs involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation.
  • a conformal p-GaN layer (using a novel Mg solid-state diffusion method and/or epitaxy) at the sidewalls of the formed structures can ensure or increase lateral hole injection in addition to the vertical injection. Therefore, volumetric hole injection can be obtained, which may in turn improve the efficiency droop through a reduction in carrier density for a given current density J.
  • the present disclosure further describes a device (e.g., LED structure) where the active region is p-type doped, with doping either in the quantum wells (QWs), the quantum barriers (QBs), or both (with either uniform or delta doping).
  • QWs quantum wells
  • QBs quantum barriers
  • the doping of QBs having the possible advantage of better QW material quality as QW quality often degrades with doping.
  • LEDs or lasers with p-type doped MQWs have been well studied in the AlInGaAs material system due to their high modulation bandwidth. In addition, this often comes with diminished threshold currents. If used in the usual geometry of contacting the extreme layers of the MQW layer stack, the usual issue of inhomogeneous hole injecting across the stack of QWs as in undoped MQW structures would occur.
  • Novel LED designs described herein include the MQW active region fully or partially p-type doped surrounded by p-type lateral injectors to effectively make a p-type active region hole injector box. Locating the active QWs in the p-side of the junction eliminates the issue related to hole injection in conventional LEDs, where the active QWs are located in the unintentionally doped (UID) region of the junction (between p- and n- regions).
  • UID unintentionally doped
  • a device comprising: a III-V light-emitting diode (LED) or III-V laser comprising intentional V- defects and a planar hole waveguide.
  • the III-V LED or III-V laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region.
  • the device example 2 wherein a thickness and composition of the alloy barrier interlayer forms a barrier suppressing transfer of the holes into the quantum wells, increasing hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer. 4. The device of example 2, wherein one or more of the repeat units comprise another alloy barrier interlayer on another side of the QB to improve waveguiding of the holes. 5.
  • the LED or laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises a delta-doped layer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region.
  • the delta-doped layer comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of holes into the QW, leading to a longer lateral diffusion of the holes in QBs before being captured by the QWs. 7.
  • the repeat units include another delta-doped layer on another side of the QB to improve waveguiding of the holes.
  • the delta doped layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer.
  • the active region comprising multi quantum wells, an n-type layer for providing electrons to the active region; and an unintentionally doped or n-type doped AlGaN layer between the n-type layer and the active region. 10.
  • V-defects comprise V-shaped lateral injectors comprising a superlattice structure coupled to the quantum wells in the active region.
  • V-shaped lateral injectors comprise V-shaped features on a patterned dielectric or a metal mask.
  • the LED or laser comprises a III-nitride LED or III-nitride laser.
  • a device comprising: an array of three dimensionally (3D) engineered structures each comprising an active region comprising III-V material and a plurality of quantum wells; and a vertical junction and a lateral junction with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction.
  • the device of example 13 further comprising a p-type layer on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region.
  • the p-type layer comprises p-type dopants diffused from a dopant layer deposited on the p-type layer.
  • the III-V layer comprises GaN
  • the p-type layer comprises p-type GaN
  • the dopant layer comprises a Magnesium layer
  • the p-type dopants comprise Magnesium.
  • the hole blocking layer comprises AlGaN, InAlN, or InAlGaN. 20.
  • the hole blocking layer comprises an n-type delta doped III-V layer.
  • the device comprises a laser or light emitting diode and the III-V material and III-V layer comprise III-nitride.
  • the sidewalls are inclined at an angle of less than 45 degrees, or at an angle between 45 degrees and 60 degrees, with respect to a base of the 3D engineered structures so as to increase surface area contact of the quantum wells with the p-type layer.
  • the 3D engineered structures have the sidewalls forming a convex or concave geometry. 24.
  • the sidewalls have a truncated triangular shape, or the 3D engineered structures comprise a pyramidal shape.
  • the active region comprises a plurality of QWs and QBs and the QWs and/or the QBs are p-type doped.
  • the device of any of the examples 13-25 further comprising an unintentionally doped (UID) layer below the active region comprising multi quantum wells, the UID layer comprising: a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN, or a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN.
  • the QBs comprise delta doping or modulation doping.
  • PIC photonic integrated circuits
  • the device is a light emitting device, a solar cell, a detector, or a transistor.
  • the device comprises a planar or a core shell structure, the core shell comprising the p-type layer forming a shell on a core comprising the active region, the device formed using a top-down or bottom-up geometry.
  • the device comprises a transistor useful in a power electronics application. 35.
  • a device useful in a power electronics application comprising: an array of three dimensionally (3D) engineered structures each comprising III-V material and a p-n junction between a p-type layer and an n-type layer; the p-n junction comprising a vertical junction and a lateral junction, wherein holes are injected through the vertical junction and the lateral junction.
  • 3D three dimensionally
  • FIG. 1 Schematic of a typical planar LED structure for vertical injection, comprising top and bottom injecting GaN layers of n- or p- type respectively, and an active multi-quantum well (MQW) region, made of alternate InGaN (quantum wells or QWs) and GaN (quantum barriers or QBs) layers, with (b) band profile 1 along cut ⁇ .
  • LEDs often include a p- type AlGaN barrier before the top p-doped GaN layer.
  • Cut (d) shows three types of hole injection pathways in proximity to the V-defect sidewall: the first, from the top p-layer, mainly in the top QW; the second and third, quasi-homogeneous for all QWs and QBs edges near the V-defect, from holes injected in the QWs and QBs.
  • the hole population originating from QWs or barrier injection through the V-defect sidewalls has decayed due to the short lateral hole diffusion length in the QWs and QBs.
  • Band diagrams in cut shows homogeneous hole injection from the QBs to the QWs throughout the V- injector, indicating long-range hole injection in all QWs using PHW structures.
  • the electrons are being injected from the n-side of the structure in cut and they can propagate through the AlGaN layer in (b) or Si ⁇ -doped layer in (c) by thermionic emission or tunneling to the QWs.
  • An additional feature could be a thicker AlGaN or d-doped barrier on the n-side of the active region to prevent or reduce direct hole injection in the n-layer, which would be detrimental to QW injection (Figure 5).
  • Figure 5 5.
  • the first layer below the first QW could be an unintentionally doped or n-type doped AlGaN layer of sufficient thickness or a Si ⁇ -doped layer of sufficient doping level and thickness to play the role of a blocking barrier to hole transport directly to the n- side.
  • Figure 6(a) Cross-sectional schematic of a final processed LED device structure that incorporates V-shaped lateral injectors (VLIs) and planar hole waveguides (PHWs).
  • VLIs V-shaped lateral injectors
  • PGWs planar hole waveguides
  • FIG. 8 Schematic of a V-defect MQW LED structure with vertical and lateral hole injections (a) without and (b) with a blocking barrier layer (either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer) to prevent or reduce direct hole injection to the n-side of the junction.
  • a blocking barrier layer either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer
  • Mg diffusion process flow (a) unintentionally doped (UID) or lightly doped GaN growth, (b) deposition of Mg layer and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ⁇ C to 1000 ⁇ C), (f) removal of the metal and Gallide from the surface.
  • Figure 12. Schematics of a simplified pyramidal structure after (a) Mg diffusion, and followed by (b) short and (c) long MOCVD or MBE grown p-GaN to achieve coalescence, i.e. planarized overgrowth over the pyramids. The coalesced structures may lead to an easier post-growth device fabrication process while may slightly increase the p-type resistance due to a thicker p-GaN.
  • Figure 13 Schematics of a simplified pyramidal structure after (a) Mg diffusion, and followed by (b) short and (c) long MOCVD or MBE grown p-GaN to achieve coalescence, i.e. planarized overgrowth over
  • underlying blocking barrier layer either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta- doped layer.
  • the length of the p-GaN sidewalls, the thickness and composition of the alloy barrier layer or thickness and doping level of the n-type delta doped layer could be designed to effectively block the holes but not limiting the electron transport and injection to the p-side. Similar methods can be applied to other geometries shown in Figure 9. Figure 14.
  • FIG. 14 Cross-sectional schematics of fully processed LEDs with engineered (a) triangular and (b) rectangular hole injector designs.
  • the p- side of the LED junctions can be made using Mg diffusion to the InGaN/GaN MQW structures or a regrown UID GaN layer, as shown in Figure 14.
  • the structures shown here utilizes both shorter sidewall p-GaN and underlying blocking barrier layer (either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer) to eliminate any leakage associated with direct hole injection from the sidewall p-GaN to the n-side of the junction.
  • Figure 15(c). Flowchart illustrating a method of making a device.
  • Figure 16 Cross-sectional schematics of nanostructure-based LED structures with (a) planar and (b) core-shell QWs/QBs using top-down and bottom-up approaches. In both cases, the p-GaN can be uniformly formed using Mg solid state diffusion described in Figure 5 and throughout this invention.
  • the core-shell geometry shown in (b) has an additional advantage of ultra-large active region volume, which can further reduce the effective carrier density and efficiency droop.
  • Figure 17. Cross-sectional schematic of an approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process for a bottom-up core- shell nanostructure geometry: (a) core-shell active region growth, (b) core-shell regrowth of a UID layer, (c) conformal deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 11, and (d) formation of a core-shell 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and Gallide layers.
  • the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction.
  • a similar approach can be applied, which would be similar to the method described in Figure 14.
  • Cross-sectional schematic of a process to fabricate fully lateral p-n junctions including (a) n-GaN growth, (b) mesa isolation etch, (c) dielectric deposition, (d) conformal deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 11, (e) formation of a p-GaN column by Mg diffusion method followed by removal of the metal and Gallide layer, and (f) conformal deposition of the p- and n-contacts.
  • the widths of the p-GaN and n-GaN are arbitrary in this method, which provides a platform for p-n junctions with extreme dimensions which are not normally possible by vertical designs.
  • FIG. 19 Cross-sectional schematic of a (a) standard planar MQW LED with UID active region and (b) LED with a design according to the present invention comprising p-type doped active region and lateral hole injection. Note that the QBs are p-type doped in (b) but due to the modulation doping, the QWs become p-type active, as indicated by the arrows.
  • Figure 20 Schematics of hole injection in standard planar vertical MQW LED with (a) UID active region, (b) p-type active region, and (c) LED with a p-type active region and a lateral injector design as described in the present invention.
  • FIG 21 Vertical band diagram schematics of LED design with (a) UID MQW active region and (b) p-type MQWs active region according to the present invention. Note that the holes are abundant in the QWs in the design in (b) and electrons would easily pass the junction and recombine in the QWs in forward bias.
  • Figure 22 Schematics of an active region consisting of QWs and QBs with the QBs being doped by Mg using (a) uniform doping and (b) delta doping.
  • Figure 23 Cross-sectional SEM images of GaN samples etched using (a) dry etching and (b) dry etching plus wet etching using Tetramethylammonium hydroxide (TMAH).
  • TMAH Tetramethylammonium hydroxide
  • FIG. 24 Mg diffusion process flow: (a) UID or lightly doped GaN growth, (b) deposition of Mg layer or Mg compound layer such as MgF2 and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ⁇ C to 1000 ⁇ C), (f) removal of the metal and Gallide from the surface.
  • Figure 26 Mg diffusion process flow: (a) UID or lightly doped GaN growth, (b) deposition of Mg layer or Mg compound layer such as MgF2 and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ⁇ C to 1000 ⁇ C), (f) removal of the metal and Gallide from the surface.
  • Figure 26 Mg diffusion process flow: (a) UID or lightly doped GaN growth, (b) deposition of Mg layer or Mg compound layer such as MgF2 and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ⁇
  • Cross-sectional schematic representation of a method to avoid direct hole injection from p-GaN sidewalls to the n-GaN by a conformal dielectric passivation prior to Mg diffusion (a) active region growth, (b) mesa etch and conformal dielectric deposition, (c) deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 6, and (d) formation of the 3D p- GaN over the active region by Mg diffusion method followed by removal of the metal and gallide layers.
  • Figure 26 Cross-sectional schematic of a few different designs for the geometry of the p-type active region, the mesa etch depth and using underlying layer to avoid direct hole injections into the n-side of the junction.
  • the shallow etch depth above the first QW prevents or reduces direct injection of holes to the n-region.
  • Controlling of the length of the p- GaN sidewall (a-c) can also be considered as it will have similar effects on the leakage as the mesa etch depth control.
  • the blocking barrier layer in (e) and (f) would serve as a hole blocking layer to avoid direct injection of holes to the n-side of the junction and to avoid current leakage.
  • GaN and its ternary and quaternary compounds incorporating aluminum and indium are commonly referred to using the terms (Al,Ga,In)N, III-nitride, III-N, Group III-nitride, nitride, Group III-N, Al(1-x-y)InyGaxN where 0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 1, or AlInGaN, as used herein.
  • compositions including stoichiometric proportions as well as “off- stoichiometric” proportions (with respect to the relative mole fractions present of each of the (Ga, Al, In) component species that are present in the composition), can be employed within the broad scope of the invention. Accordingly, it will be appreciated that the discussion of the invention hereinafter in primary reference to GaN materials is applicable to the formation of various other (Al, Ga, In)N material species. Further, (Al,Ga,In)N materials within the scope of the invention may further include minor quantities of dopants and/or other impurity or inclusional materials. Boron (B) may also be included.
  • III-V materials or devices are equivalent and broadly construed to include respective compounds or compositions comprising Group III and Group V species, e.g., but not limited to, binary, ternary and quaternary compositions of such Group III species combined with Group V species, where Group III, III, Group V, V refer to groups in the periodic table of the elements.
  • One approach to eliminating the spontaneous and piezoelectric polarization effects in GaN or III-nitride based optoelectronic devices is to grow the III-nitride devices on nonpolar planes of the crystal. Such planes contain equal numbers of Ga (or group III atoms) and N atoms and are charge-neutral.
  • nonpolar III-nitride is grown along a direction perpendicular to the (0001) c-axis of the III-nitride crystal.
  • Another approach to reducing polarization effects in (Ga,Al,In,B)N devices is to grow the devices on semi-polar planes of the crystal.
  • semi-polar plane (also referred to as “semipolar plane”) can be used to refer to any plane that cannot be classified as c-plane, a-plane, or m-plane.
  • a semi-polar plane may include any plane that has at least two nonzero h, i, or k Miller indices and a nonzero l Miller index.
  • Some commonly observed examples of semi-polar planes include the (11-22), (10-11), and (10-13) planes.
  • Other examples of semi-polar planes in the wurtzite crystal structure include, but are not limited to, (10-12), (20-21), and (10-14).
  • the nitride crystal’s polarization vector lies neither within such planes or normal to such planes, but rather lies at some angle inclined relative to the plane’s surface normal.
  • the (10-11) and (10-13) planes are at 62.98° and 32.06° to the c-plane, respectively.
  • Current droop refers to the reduction in the efficiency of GaN-based LEDs at high injection levels 1 . Auger non-radiative recombination has recently been revealed to be the origin of the current droop 2 , as it increases faster than the radiative emission rate with carrier densities.
  • top QWs the QWs that are grown nearest to the p-GaN layer, as the growth sequence of a basic LED structure is n-GaN followed by QWs followed by p-GaN.
  • holes have poor vertical transport properties, which prevents them from reaching down to the deeper QWs near the n-side of the junction.
  • LEDs green, yellow and red LEDs
  • the limitation of hole transport leads to a very inhomogeneous current injection.
  • the top QWs receiving most of the hole current (Figure 1) have large joint electron and hole carrier densities and hence large Auger non-radiative recombination, leading to significant droop. This effect is largely independent of the number of QWs, as most QWs are inactive for light emission due to the lack of holes.
  • methods of carrier injection in the whole active volume called hereafter volumetric carrier injection, are of substantial interest as they would lead to low-droop GaN-based LEDs emitting at any wavelengths.
  • V-shaped defects commonly referred to as V-defects
  • V-shaped lateral injectors VLIs
  • VLIs V-shaped lateral injectors
  • PGW planar hole waveguide
  • Figure 4 we propose an engineered planar hole waveguide (PHW) design to enhance the laterally injected minority hole diffusion length in the QBs ( Figure 4) by introducing (i) thin AlGaN interlayers or (ii) thin Si-delta doped GaN layers near or just below each of the QWs.
  • the thickness and composition of the AlGaN layer is engineered to ensure or increase long range hole diffusion in the QBs before holes are captured by the QWs via tunneling or percolative transport through the disordered AlGaN layer ( Figure 4(b)).
  • the band-bending associated with the high doping at the QW/QB interface provides a barrier to the hole injection, leading to longer lateral diffusion of the holes in QBs before being captured by the QWs ( Figure 4(c)).
  • the doping level of the Si-doped GaN layer and the exact position in the QBs with respect to the QWs are design considerations. Note that the introduced Si delta doping would have negligible effects on the sidewall doping as the sidewall semipolar ⁇ 10-11 ⁇ planes have significantly lower Si incorporation compared to c-plane.
  • the QBs can be made of InGaN which will lower the injection barrier from the p- type injection layer.
  • the lower barriers can be made of homogeneous InGaN material, graded InGaN material, quaternary materials of the InGaAlN materials family, or a superlattice made of the InGaAlN materials family.
  • the thickness of QBs with respect to the thickness of QWs can also be designed to increase the total volume of the QBs and to improve the hole injection in the QBs relative to the direct hole injection in the QWs.
  • the QBs can also be modulation doped by Mg delta doping to reduce the injection barrier in the QBs to improve the hole injection in the QBs relative to the direct hole injection in the QWs.
  • Figure 4 shows the band diagrams for LEDs with VLIs, and with VLIs plus PHWs. The concept is to induce long-range lateral transport of minority holes injected into engineered QBs to ensure or increase volumetric injection.
  • volumetric hole injection the proposed design would significantly reduce the local p in active QWs for a given total J and thus lead to droop reduction.
  • the first layer below the first QW could be an unintentionally doped or n-type doped AlGaN layer of sufficient thickness to play the role of a blocking barrier to hole transport directly into the n-side.
  • a Si delta-doped layer of sufficient doping level and thickness can also be used to serve as blocking barrier to hole transport directly into the n-side.
  • Preferred ways of obtaining shape- and density-controlled V-shaped lateral injectors can include, but are not limited to, using (i) pre-active region InGaN/GaN superlattice stacks or (ii) ex-situ dielectric or metal mask using high-resolution imprint/lithography followed by metal-organic chemical vapor deposition (MOCVD).
  • MOCVD metal-organic chemical vapor deposition
  • thickness, composition, and growth conditions of the stack are design parameters.
  • various mask patterns including circles and stripes with different openings and pitch sizes can be applied.
  • For the stripe patterns various orientations of stripes can be used. Intentionally high density of VLIs followed by PHW approach can significantly mitigate the droop in all wavelengths.
  • FIG. 6 shows a schematic of a fully processed LED with VLIs and PHWs.
  • the advantages of these LED structure designs include (i) reduced droop by reduction of p in the active region, (ii) improved spatial uniformity of the emission due to the more uniform hole injection, (iii) industrial compatibility, and (iv) ease of implementation.
  • Additional design parameters include: the relative thicknesses of QWs and QBs, the composition and thickness of the AlGaN layer, the doping and position of Si delta- doped layers, the eventual addition of another AlGaN and/or delta Si-doped GaN layer on the other side of each QB to improve hole waveguiding, and the density and geometry of VLIs.
  • This method can be applied to all wavelengths by changing the active region bandgap.
  • White light can also be generated on a single LED on a single chip using stacks of red-green-blue-yellow (RGBY) QWs in a single LED on a single chip.
  • RGBY red-green-blue-yellow
  • the white LEDs developed using this technique would provide higher efficiency and higher modulation bandwidths compared to the conventional phosphor converted blue LEDs (which rely on phosphor conversion which is a very inefficient and slow process) for solid-state lighting and visible-light communication.
  • This injection method can be similarly applied to other III-nitride light emitting structures such as UV LEDs and lasers. The method can be applied to light emitting structures with different crystal orientations.
  • a III-nitride light-emitting diode comprising intentional V-defect formation and a planar hole waveguide and method of making the same.
  • the method of embodiment 1, using substrates with polar c-plane, either Ga-face or N-face, and/or nonpolar and/or semipolar orientations.
  • different patterns including circles and stripes with different opening and pitch sizes and stripe orientations can be used. 12. Different densities of V-shaped lateral injectors can be used to further enhance the hole lateral injection. 13. An engineered large number of QWs for very high active region volume to enhance efficiency and reduce droop. 14. The method can be applied to all wavelengths by changing the active region bandgap. 15. Method of white light generation using stacks of RGBY QWs in a single LED on a single chip by stacking QWs emitting at different wavelengths, wherein the stack is laterally injected. 16. The method can be applied to other III-V material systems. 17. The method can be applied to other structures such as UV LEDs and lasers. 18.
  • the PHW comprises a delta doped layer and/or an alloy barriers having a doping and/or alloy composition suitable for waveguiding the holes.
  • Figure 6(a)-6(b) illustrate a method of making a device 600, comprising: growing a III-V light-emitting diode (LED) 602 or III-V laser comprising intentional V-defects (VLI) and a planar hole waveguide (PHW). 2. The method of example 1, further comprising growing the III-V LED or III-V laser on a substrate 604 having a polar c-plane, either Ga-face or N-face, a nonpolar, and/or a semipolar orientation. 3.
  • LED III-V light-emitting diode
  • VLI intentional V-defects
  • PHW planar hole waveguide
  • any of the preceding examples further comprising growing the III-V LED or III-V laser, including the V-defects and the planar hole waveguide, by metalorganic chemical vapor deposition.
  • Figure 5 and Figure 6(a)-6(b) illustrate the method of any of the previous examples, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide comprising an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 5.
  • QW quantum well
  • QB quantum barrier
  • the method of example 4 further comprising growing a thickness and a composition of the alloy barrier interlayer so as to form a barrier suppressing transfer of the holes into the QWs, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer.
  • the method of example 4 or 5 further comprising, in one or more of the repeat units, another alloy barrier layer on the other side of the QB to improve waveguiding of the holes.
  • the alloy barrier comprises AlGaN or InAlN or InAlGaN. 8.
  • Figure 5 and 6(a)-6(b) illustrate the method of examples 1-7, wherein the growing comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide comprising a delta-doped III-V layer 610 in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region.
  • QW quantum well
  • QB quantum barrier
  • the delta-doped layer 610 comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of the holes into the QW, the barrier increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling through the doping layer.
  • the method of example 9 further comprising growing, in one or more of the repeat units, another delta-doped III-V layer on the other side of the QB to improve waveguiding of the holes. 11.
  • the delta doped III-V layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer.
  • Figure 6(a)-6(b) illustrates the method of any of the preceding examples, wherein the growing comprises: growing the active region 606 comprising multi quantum wells, growing an n-type layer 608 for providing electrons to the active region; and growing an unintentionally doped or n-type doped AlGaN layer 608 between the n-type layer and the active region. 13.
  • FIG. 650 illustrates the method of any of the preceding examples, further comprising: forming intentional V-shaped lateral injectors (VLI) using a patterned dielectric or metal mask, as illustrated in block 650; after forming the V-shaped lateral injectors, optionally growing V-shaped features on the patterned dielectric mask so as to control a size and density of the V- shaped lateral injectors (as illustrated in Block 652); and growing the III-nitride LED or III-V laser on the V-shaped lateral injectors, as illustrated in block 654. 15.
  • VLI intentional V-shaped lateral injectors
  • dielectric or metal mask includes a pattern comprising circles and/or stripes, the method further comprising selecting a pitch, dimensions, and an orientation of the circles and/or stripes.
  • the method of examples 14 or 15 further comprising selecting a density of the V-shaped lateral injectors so as to enhance or tailor the lateral injection of the holes into the active region.
  • the method of any of the preceding examples further comprising selecting a larger number of quantum wells in the active region of the LED or laser so as to increase a volume of the active region and enhance or tailor efficiency and reduce current droop of the LED or laser.
  • the method of any of the preceding examples further comprising selecting the composition of the active region so as to obtain the LED or laser emitting electromagnetic radiation having any visible wavelength. 19.
  • Figure 5 and Figure 6(a) illustrates the method of any of the preceding examples, further comprising: growing the active region 604 of the LED or laser comprising a stack of quantum wells (QW), each of the quantum wells configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength; and wherein the stack is laterally injected with holes.
  • the LED or laser comprises a III-nitride LED or III-nitride laser.
  • Figure 6(a) illustrates a device 600, comprising: a III-V light-emitting diode (LED) 602 or III-V laser comprising intentional V-defects (VLI) and a planar hole waveguide (PHW) (e.g., V-defects on or above, connected to, or coupled to, the planar hole waveguide).
  • LED III-V light-emitting diode
  • PGW planar hole waveguide
  • Figure 6(a) further illustrates the device of example 22, wherein the III-V LED or III-V laser comprises: an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region.
  • the III-V LED or III-V laser comprises: an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region.
  • a thickness and composition of the alloy barrier interlayer forms a barrier suppressing transfer of the holes into the quantum wells, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the Q
  • the LED or laser comprises: an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises a delta-doped layer 610 in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region.
  • the delta-doped layer comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of holes into the QW, leading to a longer lateral diffusion of the holes in QBs before being captured by the QWs.
  • one or more of the repeat units include another delta-doped layer on the other side of the QB to improve waveguiding of the holes. 29.
  • the delta doped layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer.
  • the device of any of the preceding examples 22-29 further comprising: an active region 606 comprising multi quantum wells, an n-type layer 608 for providing electrons to the active region; and an unintentionally doped or n-type doped AlGaN layer 610 between the n-type layer and the active region.
  • 31. The device of any of the examples 22-30, further comprising intentional V-shaped lateral injectors VLI comprising a superlattice structure coupled to quantum wells in the active region.
  • the V-shaped lateral injectors comprise V-shaped features on a patterned dielectric or metal mask.
  • the LED or laser comprises a III-nitride LED or laser.
  • FIG. 34 The device or method of any of the preceding examples, wherein the holes recombine with electrons in the active region or quantum well so as to emit electromagnetic radiation comprising visible, infrared, or ultraviolet wavelengths.
  • Figure 6(c) and 6(a) illustrate the method or device of any of the previous examples, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide PHW comprising a III-nitride interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region, wherein: a composition and thickness of the III-nitride interlayer is selected to form a barrier suppressing transfer of the holes into the QWs, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the Al
  • the active region comprises quantum wells (QWs) having quantum barriers (QBs) confining electrons and holes in the quantum wells, and the QBs comprise InGaN so as to reduce a barrier between the QB and a p- type injection layer, wherein the barrier comprises a barrier for holes being injected from the p-type layer to the QB.
  • the InGaN comprises homogeneous InGaN material, graded InGaN material, quaternary materials of the InGaAlN materials family, or a superlattice including InGaAlN. 38.
  • a thickness of the QBs with respect to a thickness of QWs is designed to increase a total volume of the QBs and to increase injection of the holes into the QBs relative to a direct injection of the holes into the QWs.
  • the QBs are modulation doped by Mg delta doping to: reduce the barrier for the holes being injected into the QBs from the p-type injection layer, and increase injection of the holes into the QBs relative to a direct injection of the holes into the QWs. 40.
  • the hole blocking layer comprises an unintentionally doped or n-type doped AlGaN layer of sufficient thickness, or an Si delta-doped layer of sufficient doping level and thickness.
  • Figure 6(a) and block 656 of Figure 6(c) illustrate the method or device of any of the previous examples 1-41, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide PHW comprising: an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region and/or a delta-doped III-V layer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region.
  • QW quantum well
  • QB quantum barrier
  • V-shaped defects (commonly referred to as V-defects) have recently markedly improved the efficiency of LEDs, particularly in the yellow and green wavelengths, by diminishing their forward voltage and hence improving their wall-plug efficiency.
  • the efficiency droop is not reduced compared to standard LEDs. This is due to the fact that, while all quantum wells (QWs) of the active layer are laterally injected thanks to the V-defects, they are only active on a short length determined by the hole diffusion length in the QWs from their injection point. An engineered structure is thus necessary to optimize the lateral hole injection to ensure or increase volumetric injection throughout the QWs, thereby reducing the efficiency droop.
  • QWs quantum wells
  • the hole diffusion length in the QWs cannot be readily improved as it is determined by electron-hole recombination.
  • the hole diffusion length in the QB is determined by the downfall of holes into the adjacent QWs.
  • PW planar hole waveguide
  • Engineered three dimensional carrier injectors for indium aluminum gallium nitride devices As described herein, hole injection is vertically inhomogeneous throughout the stack of QWs and only the top QWs, near the p-side of the LED heterostructure are populated by holes 4,5 (in the remainder of this description, we call bottom QWs, the QWs that are grown nearest to the n-GaN layer, as the growth sequence of a basic LED structure is n-GaN followed by QWs followed by p-GaN) due to their larger effective mass compared to electrons. In longer wavelength LEDs, the larger internal polarization fields put a larger energy barrier to the hole transport.
  • V-shaped defects (commonly referred to as V-defects) have recently markedly improved the wall-plug efficiency of LEDs, particularly in the yellow and green wavelengths 6 by reducing their forward voltage.
  • FIG. 7 Schematics of a V-defect in a multi- QW LED structure is shown in Figure 7. The improvement is attributed to the lateral hole injection obtained at the oblique (relative to the overall growth direction) plane of the V-defect.
  • the lateral injection in the V-defect is local due to the smaller energy discontinuities between the QWs and the quantum barriers (QBs) for carriers travelling form the oblique p-type doped region, as schematically shown in Figure 8.
  • QBs quantum barriers
  • 3D engineered structures we shall call such structures three dimensionally (3D) engineered structures to differentiate them from the usual LED structures which rely on planar geometries.
  • 3D engineered structures the geometries of active layers and contacts do not lie in the same or parallel planes as in planar structures.
  • the proposed designs involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation (Figure 9).
  • the active region structure designs are shown in Figure 9.
  • the structures are formed using a top-down approach in which a combination of dry, either inductively coupled plasma (ICP) or reactive ion etching (RIE), and wet etching (using KOH-based solutions such as AZ400K, AZ300MIF, TMAH, etc.) are used.
  • ICP inductively coupled plasma
  • RIE reactive ion etching
  • KOH-based solutions such as AZ400K, AZ300MIF, TMAH, etc.
  • a photoresist reflow method is applied to obtain angled facet etch patterns with different inclination angles.
  • the inclination angles are controlled by the photoresist geometry which is controlled by the heating and consequently reflow condition.
  • a conformal p-GaN layer (using epitaxy or solid-state diffusion method described below) at the sidewalls of the formed structures would ensure or allow or increase lateral hole injection in addition to the vertical injection. Therefore, a volumetric hole injection is obtained, which improves the efficiency droop as it could reduce carrier density for a given J.
  • Such designs leading to sidewall injection scheme hereafter called 3D injectors, can be formed by a combination of dry and wet etching process.
  • a photoresist reflow 7 method can be used to form different pattern shapes.
  • the photoresist reflow method is a method to generate 3D structures by applying heat to the photoresist. First, a conventional photoresist pattern is generated on a sample. Then, by applying heat to the sample, the photoresist pattern is thermally treated above melting temperature of the photoresist. A convex shape is formed due to a strong surface tension of the liquid resist and the surface property of the sample. The convex geometry allows for dry etching with different facet sidewall inclination angles depending on the resist shape. The method can be used to generate different patterns with different sidewall inclination angles.
  • Figure 10 shows cross-sectional scanning electron microscopy (SEM) images of several GaN trenches with only dry etching (Figure 10(a)) and dry etching plus wet etching using TMAH ( Figure 10(b)).
  • the engineering parameters for photoresist reflow is the thickness, heating temperature and duration of the heating.
  • dry etching either using ICP or RIE
  • the etching conditions including gas flows, RF etching power, etch rates and DC bias are engineering parameters.
  • wet etching either using TMAH, AZ400K, AZ300MIF, phosphoric acid, and any other KOH-based solutions can be used.
  • the engineering parameters for wet etching include wet etch time, solution concentration and temperature.
  • Photo-induced chemical etching also called photoelectrochemical or PEC etching
  • KOH-based solutions with and without applied electrical bias
  • the initial conformal formation of p-GaN on the top and sidewalls of the mesa structures can be obtained using a novel Mg solid-state diffusion process described in Figure 11.
  • a Mg layer followed by a Pd or Pt layer is deposited on an unintentionally doped (UID) or lightly doped GaN on sapphire, Si, SiC or freestanding GaN substrates.
  • UID unintentionally doped
  • GaN unintentionally doped
  • the Mg atoms Upon elevating temperature (800 ⁇ C to 1000 ⁇ C), the Mg atoms start to diffuse to the UID or lightly doped GaN while Ga atoms migrate out of the surface toward the metallic layer and start to form a Gallide layer at the semiconductor-metal interface. Mg atoms replace Ga in the crystal and serve as acceptors. Without the need for another crystal epitaxy step, a layer of p-type GaN can therefore be obtained after removing the metal and the formed Gallide layers.
  • the structures could remain 3D for fabrication or can be coalesced during a p-GaN overgrowth layer by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) ( Figure 12).
  • MOCVD metal-organic chemical vapor deposition
  • MBE molecular beam epitaxy
  • a p-GaN layer can also be grown using NH 3 pulsed-mode MOCVD growth methods, similar to growth of core-shell nanostructures 8,9 .
  • the structures can then be processed using any standard LED processing procedure.
  • the engineering parameters for the Mg diffusion method include annealing temperature (and consequently the Mg diffusion depth) and the thicknesses of the Mg layer and the metal layers.
  • the Mg diffusion depth can also be as large as a whole triangular or rectangular mesa or trench.
  • the p-n junction formation by the Mg diffusion method should be less sensitive to the impurities from ambient exposure and the damage from dry etching at the top surface and sidewalls, since the p-n junction will form far from the top and sidewall surfaces.
  • n+ layer can be considered below the UID or lightly doped GaN layer.
  • p-i-n or p-n junctions can be formed after the Mg diffusion.
  • the length of the Mg-diffused p-type sidewall can be engineered (Figure 13(b)). This may reduce the hole injection a bit in the very first QW (the nearest QW to the n-GaN). However, the impact of slight reduction in hole injection in one QW on the overall efficiency can be insignificant, as the total number of QWs can be very large in this method.
  • the first layer could be a layer, either an alloy barrier layer such as a UID or n-type doped AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer of sufficient thickness to play the role of a blocking barrier to the hole transport to the n-side of the junction ( Figure 13(c)).
  • an alloy barrier layer such as a UID or n-type doped AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer of sufficient thickness to play the role of a blocking barrier to the hole transport to the n-side of the junction ( Figure 13(c)).
  • the length of the p-GaN sidewalls, the thickness and composition of the alloy barrier layer or thickness and doping level of the n-type delta doped layer could be engineered to minimize hole injection into the n-GaN, while maintaining high efficiency. Similar method can be applied
  • the p-GaN can be formed by Mg diffusion into a UID GaN spacer which can be overgrown on the mesa active region by MOCVD or MBE.
  • Figure 14 shows a cross-sectional schematic of this approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process.
  • the steps include active region growth ( Figure 14(a)), mesa etching ( Figure 14(b)), dielectric mask for regrowth ( Figure 14(c)), regrowth of 3D UID spacer layer ( Figure 14(d)), conformal deposition of Mg layer and metal (Pt or Pd) layer on top of the spacer layer ( Figure 14(e)), and formation of the 3D p-GaN over the active region by Mg diffusion to the regrown UID GaN spacer layer followed by the removal of the metal and Gallide layers (Figure 8(f)).
  • the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction (similar to other approaches discussed in Figure 13).
  • Figure 15 schematically shows the fully processed LEDs in two particular 3D geometries.
  • the LEDs of Figure 15 operate as follows: in spite of the shorter path between the n ++ -GaN and p-GaN layers through the UID GaN or lightly doped layer, electrons will preferentially travel through the InGaN QWs towards the p-contact. This is due to the higher built-in energy barrier of the n-GaN-p GaN junction compared to the energy barrier of the MQW heterostructure. This is clear from the turn-on voltage difference between GaN p-n junctions (about 3.2V) vs. that of MQW LEDs, typically below 2.8 V, dependent on the Indium composition in the QWs.
  • Engineering parameters include size and distribution or the mesas, convex or concave geometries (whether mesa geometry or trench geometries), number of QWs, and thicknesses of the QWs/QBs.
  • the method described herein can similarly be applied to bottom-up nanostructures as well, for either planar ( Figure 16(a)) or core-shell ( Figure 10(b)) QW/QB designs.
  • Both planar and core-shell active region geometries in the structures shown in Figure 16 can be controlled by growth conditions and thus growth kinetics and/or thermodynamics in MOCVD or MBE techniques.
  • the active regions can be grown on nanostructures using MOCVD or MBE on patterned substrates 9 .
  • the p-GaN growth is normally non- uniform in such nanostructures leading to different thicknesses of p-GaN on the top and on the sidewall of the nanostructures 8,9 .
  • the Mg solid-state diffusion (described in Figure 5) can be applied to the core-shell active region grown on the nanostructures resulting in uniform p-GaN formation across the nanostructures ( Figure 10(b)).
  • the uniform p-GaN facilitates the volumetric hole injection in the nanostructure-based light-emitting devices.
  • the p-GaN can be formed by Mg diffusion into a UID GaN spacer which can be overgrown on the nanostructure active region by MOCVD or MBE.
  • Figure 17 shows a cross-sectional schematic of this approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process.
  • the steps include core-shell active region growth (Figure 17(a)), core-shell regrowth of a UID layer (Figure 17(b)), conformal deposition of Mg layer and metal layer (Figure 17(c)), and formation of a core-shell 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and Gallide layers ( Figure 17(d)).
  • the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction. (similar to other approaches discussed in Figure 13).
  • a similar approach can be applied to the nanostructure geometries shown in Figure 16 (a) to avoid direct Mg diffusion into the active QWs during the Mg diffusion process (similar to the method described in Figure 14).
  • the presented invention can also be used to form 3D p-n junctions and to make fully lateral p-n junctions for power electronic applications.
  • Figure 18 demonstrates an approach to make 3D lateral p-n junctions with the methods described in this invention.
  • the widths of the p-GaN and n-GaN are arbitrary in this method, which provides a platform for p-n junctions with extreme dimensions which are not normally possible by vertical designs. For example, extremely wide drift regions are possible in this design which can provide very large reverse blocking voltages for power electronic applications.
  • the depths of the isolation mesa etch and the dimensions of the Mg diffused p-GaN column could be other engineering parameters.
  • III-nitride nanowire LEDs and lasers are potential building blocks for future photonic integrated circuits (PICs) and nanophotonic devices as light sources due to their tunable band gap and excellent waveguide properties.
  • PICs photonic integrated circuits
  • the proposed nanowire-based electrically injected lasers can be used in PICs and also in nanometrology 10 as cantilever for atomic force microscopy and near-field scanning electron microscopy. Solar cell or photodetector designs including the 3D engineered structures can also be considered.
  • III-nitride light-emitting diodes comprising of intentional 3D engineered structures with vertical and lateral junctions.
  • the method of example 1 wherein the junctions are formed using Mg solid-state diffusion.
  • 3. The method of example 1, wherein substrates with polar c-plane, either Ga-face or N-face, and/or nonpolar and/or semipolar orientations are used.
  • 4. The method of example 1, wherein rectangular and pyramidal geometries are used.
  • different patterns including circles and stripes with different opening and pitch sizes and stripe orientations can be used.
  • Growth of LED structures with metalorganic chemical vapor deposition 7. Top-down 3D engineered structure formation using combination of dry etching and wet etching. 8.
  • an underlying blocking barrier an alloy barrier layer such as AlGaN, InAlN, or InAlGaN
  • an underlying blocking barrier an alloy barrier layer such as AlGaN, InAlN, or InAlGaN
  • an underlying blocking barrier an n-type delta doped layer such as Si or Ge delta-doped layer
  • Figures 15-17 illustrate a device 1500, comprising: an array of three dimensionally (3D) engineered structures 1502 (e.g., a mesa) each comprising an active region 1504 comprising III-V material and a plurality of quantum wells 1506; and a vertical junction 1508 and a lateral junction 1510 with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction. 2.
  • 3D engineered structures 1502 e.g., a mesa
  • an active region 1504 comprising III-V material and a plurality of quantum wells 1506
  • a vertical junction 1508 and a lateral junction 1510 with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction.
  • the device of example 1 or 2 further comprising: an n-type III-V layer 1514 providing electrons to the quantum wells; a p-type layer 1512 on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the quantum wells on the sidewall so as to inject holes laterally into each of the quantum wells; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer 1516 between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer and the 3D engineered structures. 4.
  • the hole blocking layer comprises AlGaN, InAlN, or InAlGaN.
  • the hole blocking layer comprises an n-type delta doped III-V layer (e.g., but not limited to as Si-delta doped GaN or Ge- delta doped GaN).
  • the device 1500 comprises a laser or light emitting diode and the III-V material and III-V layer comprise III-nitride.
  • the 3D engineered structures 1502 have the sidewalls 1522 forming a convex or concave geometry.
  • the sidewalls 1522 have a truncated triangular shape, or the 3D engineered structures 1502 comprise a pyramidal shape.
  • Figure 15(c) illustrates a method of making a device, comprising: forming a device 1500 comprising three dimensionally (3D) engineered structures each comprising an active region (as illustrated in Block 1580); and forming a vertical junction and a lateral junction with each of the 3D engineered structures, wherein holes are injected into the active region through the vertical junction and the lateral junction (as illustrated in Block 1582). 14.
  • Figure 15(c) illustrates the method or device of any of the preceding examples, further comprising: patterning the 3D engineered structures with different patterns, including selecting a pitch and orientation of openings and stripes around the 3D engineered structures (the forming step of Block 1580 may include patterning the 3D engineered structures).
  • Figure 15(c) illustrates the method or device of any of the preceding examples, further comprising growing the light emitting device using metalorganic chemical vapor deposition (the forming step 1580 may include growing device layers). 19.
  • FIG. 15(c) illustrates the method or device of example 19, wherein the forming of Block 1580 comprises patterning the 3D engineered structures using photoresist, including depositing photoresist as a mask layer and reflowing the photoresist to engineer a sidewall etch angle of the 3D engineered structures during the dry etching.
  • KOH potassium hydroxide
  • Figure 9, 11, 12, 15B illustrate the method or device of any of the preceding examples, wherein forming the device (Block 1580) further comprises: growing an n-GaN layer 1514 or n-type III-nitride layer; growing the active region 1504 comprising multi quantum wells (MQW); and growing an underlying blocking barrier layer 1518 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region, and forming (e.g., patterning) the 3D engineered structures 1502 to include the active region. 24.
  • MQW multi quantum wells
  • the blocking layer comprises a barrier layer including AlGaN, InAlGaN, or InAlGaN.
  • the blocking layer comprises an n- type delta doped layer (comprising, but not limited to, a Si delta doped layer or a Ge delta doped layer).
  • Figure 12 illustrates the method or device of any of the preceding examples, further comprising engineering or selecting a length of the Mg-diffused p- GaN sidewalls or Mg-diffused III-nitride sidewalls 1522 to avoid direct injection of holes into an n-side of the junction with the active region, as illustrated in forming of junctions step of Block 1582. 27.
  • FIG. 12 illustrates the method or device of any of the preceding examples, further comprising forming p-type material 1512 at the sidewalls 1522 of the 3D engineered structures so as to achieve volumetric injection is obtained for all the wells (can be performed in the forming of junctions step 1582). 29.
  • the light emitting device comprises a micro LED
  • the 3D engineered structures reduce the size-dependent efficiency drop of the micro-LEDs in a micro-pixel display or visible light communication system.
  • the method or device of any of the preceding examples further comprising increasing a number of quantum wells in the active region 1504 so as to increase a volume of the active region, thereby enhancing or tailoring efficiency of the light emitting device and reducing current droop of the light emitting device.
  • 31. The method or device of any of the preceding examples, further comprising selecting an alloy composition of the active region 1504 so as to obtain the light emitting device emitting electromagnetic radiation having any visible wavelength. 32.
  • Figures 15B, 9, and 11-12 illustrates the method or device of any of the preceding examples, further comprising: growing the active region 1504 of the light emitting device comprising a stack of quantum wells, each of the quantum wells configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength (can be grown in the forming step of Block 1580); and wherein the stack is laterally injected with holes.
  • the light emitting device comprises a III-nitride LED or III-nitride laser.
  • the light emitting device emits ultraviolet light. 35.
  • the light emitting device comprises a top-down or bottom-up light emitting structure. 36. The method or device of any of the preceding examples, wherein the light emitting device comprises a bottom-up core-shell or a non-core-shell geometry light emitting structure. 37. The method or device of any of the preceding examples, wherein the light emitting device comprises a nanostructure-based light-emitting structures. 38. The method or device of any of the preceding examples, wherein the light emitting device comprises a III-V material system. 39.
  • Figures 15B, 9, 11-12 illustrates the method or device of any of the preceding examples, further comprising forming a p-type layer on a sidewall and a top of each of the 3D engineered structures, including (can be formed in the junction forming step of i Block 1582): growing a III-nitride layer 1100 on the top and sidewall of each of the 3D structures ( Figure 11a); depositing an Mg layer 1102 on the III-nitride layer ( Figure 11b); depositing a metal layer 1104 on the Mg layer, the metal layer including Pt or Pd ( Figure 11c); and heating the structure to a temperature above 800 degrees Celsius so as to cause diffusion of the Mg from the Mg layer into the III-nitride layer 1100, thereby forming a p-type doped layer 1106,
  • FIG. 15A-15B further illustrate the method or device of any of the preceding examples, comprising a hole blocking layer between the n-type layer and the active region, the hole blocking layer: comprising an alloy barrier layer 1518 (e.g., but not limited to, unintentionally doped or n-type doped AlGaN, InAlN, or InAlGaN) and/or or an n-type delta doped layer (e.g, but not limited to a Si or Ge delta-doped layer), and the hole blocking layer of sufficient thickness to block hole transport of holes to the n-side of the junction.
  • an alloy barrier layer 1518 e.g., but not limited to, unintentionally doped or n-type doped AlGaN, InAlN, or InAlGaN
  • an n-type delta doped layer e.g, but not limited to a Si or Ge delta-doped layer
  • the hole blocking layer can be formed/deposited during the forming of the device structure step of Block 1580).
  • Figures 12 and 15A-15B further illustrate the method or device of any of the preceding examples, comprising: the p-type layer 1512 formed on or above a top and sidewall 1522 of each of the 3D engineered structures 1502, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region, and the p-type layer 1512 formed by magnesium diffusion into an unintentionally doped III-nitride layer overgrown on the active region, the p-type layer avoiding (1) direct diffusion of Mg atoms to the quantum wells in the active region and/or (2) generation of Shockley-Read-Hall (SRH) non-radiative recombination in the active region.
  • Shockley-Read-Hall Shockley-Read-Hall
  • Figures 9-15A-15B further illustrate the method or device of example 43, wherein: fabrication of the device includes (block 1580): growing the active region, etching a mesa including the active region, depositing a dielectric mask (Block 1582 during forming of junction step 1582)); using the mask to selectively grow the III-nitride layer 1100 (e.g., GaN) on the top and the sidewalls of the mesa (during step 1582), Figure 11a conformally depositing an Mg layer 1102 and a metal 1104 (e.g., but not limited to Pt or Pd) layer on top of the III-nitride layer ( Figure 11b, step 1582), and formation of the p-type layer 1512 over the active region by Mg diffusion to the III-nitride layer ( Figure 11c, step 1582); and removing the metal layer and a Gallide layer formed during the Mg diffusion ( Figure 11f, step 1582).
  • fabrication of the device includes (block 1580): growing the active region
  • the device comprises a hetero- and homo-junction GaN-based nano laser or LED for photonics and/or nanometrology applications 46.
  • the nanolaser or nano LED comprises a III-nitride nanowire LED or a nanowire laser useful as a building block in a photonic integrated circuits (PIC) or as a light source.
  • PIC photonic integrated circuits
  • the device is a light emitting device, a solar cell, a detector, or a transistor.
  • the light emitting device 1500 emits light in response to electrons recombining with holes in the active region 1504, the electrons provided from the n-type layer and the holes provided from the p-type layer, or the active region in the device comprising the solar cell generates holes and electrons in response to electromagnetic radiation absorbed in the active region.
  • the device comprises a planar or a core shell structure, the core shell comprising the p-type layer forming a shell on a core comprising the active region, the device formed using a top- down or bottom-up geometry.
  • the device comprises a transistor useful in a power electronics application. 51.
  • Figure 18 illustrates a device 1800 useful in a power electronics application (e.g., transistor), comprising: an array of three dimensionally (3D) engineered structures 1802 (e.g., a mesa) each comprising III-V material and a p-n junction 1804 between a p-type layer/region 1806 and an n-type layer/region 1808; the p-n junction comprising a vertical junction 1810 and a lateral junction 1812, wherein holes are injected through the vertical junction and the lateral junction.
  • 3D three dimensionally (3D) engineered structures 1802 (e.g., a mesa) each comprising III-V material and a p-n junction 1804 between a p-type layer/region 1806 and an n-type layer/region 1808; the p-n junction comprising a vertical junction 1810 and a lateral junction 1812, wherein holes are injected through the vertical junction and the lateral junction.
  • Figure 18 further illustrates a method for fabricating the device of example 51, comprising fabricating a transistor including the p-n junction and having a drift region sufficiently wide to provide very large reverse blocking voltage desirable for power electronic applications, the method further comprising tailoring an isolation mesa etch used to fabricate the 3D engineered structures and the dimensions of a Mg diffused p-GaN layer formed on the p-type layer.
  • the advantages of the LED structure designs described herein include (i) low- droop InGaN-based RGBY LEDs by volumetric hole injection, (ii) more design freedom for thick active regions with large number of QWs for high efficiency, (iii) improved efficiency of green LEDs and contribute to solve the green gap, and (iv) mitigation of the size-dependent efficiency drop in micro-LEDs due to the reduced surface effects.
  • the designs described herein may also partially increase lateral optical confinement in the active region.
  • the triangular/pyramidal geometry has the advantage of redirecting photons towards the extraction cone of the substrate/air interface, the more so with angle optimization.
  • the position of the junctions within the MQWs can be adjusted by the duration and temperature of the Gallide process, to optimize uniformity of carrier injection.
  • a thicker p-GaN can also be grown by MOCVD/MBE on top of the p-GaN obtained by Mg diffusion method to planarize the structure for ease of processing ( Figure 6).
  • An engineered large number of QWs for all wavelengths can be used in the active region without the issues with hole injections in the deeper wells.
  • white LEDs on a single wafer can be obtained by designing active RGBY QWs with different emission colors on a single structure on a single chip.
  • the white LED processed using this method has the advantage of higher efficiency and higher modulation bandwidth compared to any conventional phosphor-converted white LEDs (with inefficient and slow phosphor conversion process) and can be used in solid-state lighting as well as visible-light communications.
  • the method can be applied to light emitting structures with different crystal orientations. This method can be similarly applied to other III-nitride light emitting structures such as UV LEDs, and lasers.
  • An application of the method in electrically injected nanostructures can be used in PICs and nanometrology.
  • the method can be used in 3D p-n diodes for fully lateral p-n junctions for power electronics. Solar cell or photodetector designs including the 3D engineered structures can also be considered based on this invention.
  • the design ( Figure 19 (b)) according to the present invention comprises a top-down approach, including a combination of dry and wet etch to fabricate the structures, and conformal p-GaN formation using a Mg solid-state diffusion approach described below.
  • the QWs and/or QBs can be doped by Mg during the metal-organic chemical vapor deposition (MOCVD) growth prior to the mesa formation. Doping the QBs is more favorable to avoid Mg acting as non- radiative defect centers within the QWs.
  • the profile of the p-type doping can be either uniform doping or modulation doping. With modulation doping, we can consider delta doping of Mg (a thin but high-concentration layer of dopant) in the QB regions. Engineering parameters for the modulation doping include the thickness, position with respect to the edges of the QBs, and doping levels.
  • Figure 21(a) shows a design according to the present invention where all the QWs are located in the p-side of the junction and all the QWs are populated by holes as they are the majority carriers in the p-side. As a result, all the QWs can contribute to the recombination process and thus improve the efficiency and efficiency droop.
  • the electron density would be high in all the QWs due to the ability of electrons to transport from one QW to another.
  • Either a p-n diode or a p-i-n diode can be used.
  • the doping levels in both sides of the junction can be tailored to engineer the depletion width (Figure 21) for a given applied bias.
  • a UID layer between the p- and the n-region can be included as shown in Figure 21(b) (indicated as UID depletion).
  • the thickness of the UID layer can be engineered to obtain optimum electron transport to the p-side of the junction.
  • the UID layer below the active MQW region could contain a superlattice to improve material quality, carrier injection (lower effective energy gap than GaN) and forward voltage.
  • the UID layer below the active MQW region could comprise a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection (progressively lower energy gap than GaN) and forward voltage.
  • Example Doping Profiles Figure 22(a) and (22b) illustrate two example profiles of modulation doping that can be used make the active region p-type: (i) uniform doping ( Figure 22(a)) and (ii) localized “d” doping ( Figure 22(b)). Both of the doping profiles can be implemented during MOCVD growth of the active region.
  • Example doping profiles include the QB average concentration of the Mg being similar in the two profiles, while the peak Mg concentration in the d modulation doping profile is between ⁇ 10 18 cm -3 and ⁇ 10 20 cm -3 .
  • Engineering parameters for the active region doping include the doping profile, thickness, position with respect to the edges of the QBs, and doping levels.
  • the designs described herein involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation.
  • the structures can be formed using a top-down approach in which a combination of dry etching (e.g., either inductively coupled plasma (ICP) or reactive ion etching (RIE)) and wet etching (e.g., using KOH-based solutions) may be used.
  • dry etching e.g., either inductively coupled plasma (ICP) or reactive ion etching (RIE)
  • wet etching e.g., using KOH-based solutions
  • a photoresist reflow method can also be applied to obtain angled facet etch patterns with different inclination angles. The inclination angles can be controlled by the photoresist geometry which is controlled by the heating and consequently reflow condition.
  • a conformal p-GaN layer (using epitaxy or a solid- state diffusion method described below) at the sidewalls of the formed structures would ensure or allow or increase lateral hole injection in addition to the vertical injection.
  • the lateral hole injectors can be formed by a combination of a dry and wet etching process.
  • a photoresist reflow 7 method can be used to form different pattern shapes.
  • the photoresist reflow method is a method to generate 3D structures by applying heat to the photoresist. First, a conventional photoresist pattern is generated on a sample. Then, by applying heat to the sample, the photoresist pattern is thermally treated above melting temperature of the photoresist.
  • a convex shape is formed due to a strong surface tension of the liquid resist and the surface property of the sample.
  • the convex geometry allows for dry etching with different facet sidewall inclination angles depending on the resist shape.
  • the method can be used to generate different patterns with different sidewall inclination angles.
  • Figure 23 shows cross- sectional scanning electron microscopy (SEM) results of several GaN trenches with only dry etching ( Figure 23(a)) and dry etching plus wet etching using Tetramethylammonium hydroxide (TMAH) ( Figure 23(b)).
  • the engineering parameters for photoresist reflow include the thickness, heating temperature and duration of the heating.
  • Engineering parameters for dry etching comprise the etching conditions, including gas flows, RF etching power, etch rates and DC bias.
  • TMAH, AZ400K, AZ300MIF, phosphoric acid, or any other KOH-based solutions can be used.
  • the engineering parameters for wet etching include wet etch time, solution concentration and temperature.
  • Photo-induced chemical etching also called photoelectrochemical etching or PEC
  • KOH- based solutions for example
  • electrical bias can also be used as a wet etching method.
  • Mg Solid State Diffusion The initial conformal formation of p-GaN on the top and sidewalls of the mesa structures can be obtained using a novel Mg solid-state diffusion process described in Figure 24.
  • An Mg layer or an Mg compound layer such as MgF2 followed by a Pd or Pt layer is deposited on a UID or lightly doped GaN on sapphire, Si, SiC or freestanding GaN substrate.
  • the Mg atoms start to diffuse to the UID or lightly doped GaN while Ga atoms migrate out of the surface toward the metallic layer and start to form a Gallide layer at the semiconductor-metal interface.
  • Mg atoms replace Ga in the crystal and serve as acceptors.
  • a layer of p-type GaN can therefore be obtained after removing the metal and the formed Gallide layers.
  • a post activation annealing process may be required to remove the F atoms (which might have penetrated into the layers during the diffusion process) to ensure high electrical conductivity of the p-type material.
  • a p-GaN layer can also be grown using NH 3 pulsed MOCVD growth methods, similar to growth of core-shell nanostructures 8,9 . The structures will then be processed using standard LED processing.
  • the engineering parameters for the Mg diffusion method include annealing temperature (and consequently the Mg diffusion depth), the thicknesses of the Mg layer and the metal layers.
  • the Mg diffusion depth can also be as large as a whole triangular or rectangular mesa or trench.
  • the Mg diffusion method should be less sensitive to the impurities from ambient exposure and the damage from dry etching at the top surface and sidewalls, since the p-n junction will form far from the top and sidewall surfaces.
  • the method can also be used in micro-LEDs as micro-pixel displays and visible light communication, since the size-dependent LED efficiency drop is diminished by the described method here due to the reduced surface effects.
  • either p-i-n or p-n junctions can be generated.
  • the first layer could be an unintentionally doped or n-type doped AlN, AlGaN, InAlN, or InAlGaN layer or n-type delta doped layer of sufficient thickness to play the role of a blocking barrier to hole transport ( Figures 26(e) and 26(f)).
  • the length of the p-GaN sidewalls, the mesa etch depth, the thickness and composition of the underlying barrier layer, doping and thickness of n-type delta doped layer could be engineered to minimize hole injection into the n-GaN, while maintaining high efficiency. Similar methods can be applied to other geometries. Prevention or reduction of direct Mg diffusion into the active QWs To avoid direct Mg diffusion to the active QWs by Mg solid-state diffusion, we can also perform a UID GaN regrowth on the active mesa structures to cap the active region prior to Mg diffusion (Figure 27).
  • the dielectric mask layer used for regrowth can be kept intact throughout the process as it would also avoid direct hole injection from the sidewall p-GaN to the n-side of the junction.
  • the UID regrowth can be performed by a pulsed NH3 MOCVD method 9 .
  • the growth conditions (such as temperature, pressure, V/III ratio and NH3 pulse duty cycle and on/off times) are the engineering parameters which control the shape and quality of the regrown UID layer.
  • Other controlling parameters include the mesa etch depth, dielectric mask thickness, and p-GaN sidewall length.
  • the p-GaN can be uniformly formed using Mg solid state diffusion described in Figure 24 and throughout this invention.
  • the core-shell geometry has an additional advantage of ultra-large active region volume, which can further reduce the effective carrier density and efficiency droop.
  • Example Device Structures Figure 28 shows a couple of processed LED designs using the methods described herein according to embodiments of the present invention. Arrays of the mesa structures can also be implemented to enhance the optical power, where the density and distribution of the structures are the engineering parameters.
  • the structures can be grown on various substrates, including planar and patterned Sapphire, Si, SiC, and freestanding GaN.
  • the structures can also be grown on nonpolar, semipolar or polar orientations. Either the whole active region structure can be p-type doped or part of the active region can be unintentionally doped and part of it could be p-type doped.
  • the active region will comprise InGaN/GaN or InGaN/InGaN QWs/QBs for visible emitters emitting visible light, or AlGaN/AlGaN or GaN/AlGaN QWS/QBs for ultraviolet emitters emitting ultraviolet electromagnetic radiation. So far we have targeted top-down fabricated structures. However, as mentioned, this method can similarly be applied to grown bottom-up structures as well, for either planar or core-shell QW/QB designs. In the core-shell nanostructure- based light emitting devices, the active regions can be grown on nanostructures using MOCVD or MBE on patterned substrates 9 .
  • FIG. 19(b), 20(c) and 29 illustrate a method of making a device 1900, comprising: forming a light emitting device 1902, photodetector 1902, or solar cell 1902 comprising intentionally three dimensionally (3D) engineered structures 1904 with vertical and lateral junctions 1906 (vertical junction 1906a and lateral junction 1906b).
  • Figure 29 illustrates an example wherein the method comprises forming the device structure including the 3D engineered structures (Block 2900) and forming the vertical and lateral junctions (Block 2902) with the 3D engineered structures. 2.
  • the method of example 1 further comprising locating the active region 1908 of the device in a p-side of the junction by p-type doping. 3.
  • the method of example 2, wherein the p-type doping of the active region is performed using metal-organic chemical vapor deposition.
  • the method of example 3 further comprising an unintentionally doped (UID) layer 1910 between the p- region 1912 and the n-region 1914. 5.
  • UID unintentionally doped
  • the active region 1908 comprises a multi quantum well (MQW) active region
  • the UID layer 1910 is below the MQW active region and contains a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN.
  • the active region 1908 comprises a multi quantum well (MQW) active region
  • the UID layer 1910 below the MQW active region comprises a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN. 7.
  • the p-type doping comprises performing a uniform or non-uniform p-type doping of the quantum wells (QWs) and quantum barriers (QBs) in the active region of the device.
  • the p-type doping comprises performing a uniform doping of Mg in the QBs of the active region.
  • the p-type doping comprises Mg delta doping of the QBs.
  • the method of example 2, wherein the p-type doping of the active region is performed using Mg solid-state diffusion. 12.
  • FIG. 19(b), 20(c), 24, and Figure 29 illustrates the method of any of the preceding examples, wherein forming the vertical/lateral junction 1906 in block 2902 further comprises forming a p-type layer 1918 on a sidewall 1916 and a top of each of the 3D engineered structures, including: growing a III-nitride layer 2400 on the top and sidewall of each of the 3D structures ( Figure 24a); depositing an Mg layer or Mg compound layer 2402 such as MgF2 on the III- nitride layer ( Figure 24b); depositing a metal layer 2406 on the Mg layer, the metal layer including Pt or Pd ( Figure 24c); and heating the structure to a temperature above 800 degrees Celsius so as to cause diffusion of the Mg from the Mg layer into the III-nitride layer, thereby forming a
  • Figure 29 illustrates the method of example 1, wherein forming the device structure in Block 2900 comprises forming the 3D engineered structures each comprising a mesa structure 1960, the method or step of Block 2900 further comprising depositing a conformal dielectric mask layer at the bottom corner of the mesa structures as a hole blocking layer 2600 to prevent or reduce direct hole injection to the n-side of the junction. 27.
  • Figure 20(c), Figure 26, and Figure 29 illustrate the method of any of the preceding examples, wherein forming the device structure in block 2900 further comprises: growing an n-GaN layer 1917 or n-type III-nitride layer; growing the active region 1908 comprising multi quantum wells; and growing: an underlying alloy blocking barrier layer 2600 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region, and/or an n-type delta doped layer 2600 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region.
  • an underlying alloy blocking barrier layer 2600 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region
  • the forming step 2900 further comprises patterning, etching, or forming the 3D engineered structure (e.g., mesa) in the device structure.
  • the alloy blocking layer 2600 comprises AlN, AlGaN, InAlN, or InAlGaN.
  • the III-nitride layer on the top and the sidewalls 1916 comprises an Mg diffused p-GaN layer 1918 having sidewalls and the height or thickness of the sidewalls 1916 is engineered to avoid direct hole injection into the n-side of the junction.
  • 30 The method of example 29, wherein a temperature at which the Mg diffusion is performed is controlled to obtain different diffusion depths. 31.
  • volumetric hole injection is obtained for all the QWs of the active region of the device, due to the formation of p-type material at the sidewalls of the 3D engineered structures.
  • the light emitting device comprises a micro LED
  • the 3D engineered structures reduce the size-dependent efficiency drop of the micro-LEDs in a micro-pixel display or visible light communication system.
  • 33. The method of any of the preceding examples, further comprising selecting a larger number of QWs in the active region 1908 of the device so as to increase a volume of the active region and enhance or tailor efficiency and reduce current droop of the LED or laser. 34.
  • the 3D engineered structures each include a mesa, the method further comprising shaping the mesa and top metal contact to the mesa to increase light emission directionality from the 3D engineered structures.
  • the 3D engineered structures are formed as a top-down or bottom-up light emitting structure.
  • the 3D engineered structures comprise bottom-up core-shell or non-core-shell geometry light emitting structures.
  • the method of any of the preceding examples further comprising: growing the active region 1908 of the LED or laser comprising a stack of QWs, each of the QWs configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength; and wherein the stack is laterally injected with holes.
  • the LED or laser comprises a III-nitride LED or III-nitride laser.
  • the 3D engineered structures comprise core-shell nanostructure-based light emitting structures.
  • the 3D engineered structures comprise a III-V material. 42.
  • the 3D engineered structures comprise GaN-based top-down or bottom-up nanostructure lasers for photonics applications.
  • the light emitting device comprises an LED or laser emitting ultraviolet light.
  • Figure 19(b) and Figure 20(c) illustrate a device 1900, comprising: an array of three dimensionally (3D) engineered structures 1904 each comprising an active region 1908 comprising III-V material and a plurality of QWs and QBs; and a vertical junction 1906a and a lateral junction 1906b with each of the 3D engineered structures, wherein: holes are injected into the QWs in the active region through the vertical junction and the lateral junction, and the QWs and/or the QBs are p-type doped. 45.
  • 3D three dimensionally
  • the device of example 44 further comprising a p-type layer 1914 on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region. 46.
  • the device of example 44 further comprising: an n-type III-V layer 1917 providing electrons to the quantum wells; a p-type layer 1918 on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the QWs on the sidewall so as to inject holes laterally into each of the QWs; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer 1910 between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer 1918 and the 3D engineered structures. 47.
  • the device of example 44 further comprising the active region 1908 between an n-type region 1914 and a p-type region 1912, and an unintentionally doped (UID) layer 1910 between the p- and the n-regions.
  • the p-type layer comprises p-type dopants diffused from a dopant layer deposited on the p-type layer.
  • the III-V layer 1917 comprises GaN
  • the p-type layer 1918 comprises p-type GaN
  • the dopant layer 2402 comprises a Magnesium layer
  • the p-type dopants comprise Magnesium. 50.
  • Figure 26 illustrates the device of any of the examples 44-49, further comprising a hole blocking barrier layer 2600 or n-type delta doped layer 2600 between the n-type layer and the active region 1914 so as to prevent or reduce direct hole injection to the «-side 1914 of the junction with the active region.
  • the hole blocking layer comprises AIN, AlGaN, InAIN, or InAlGaN.
  • the 3D engineered structures have the sidewalls 1916 forming a convex or concave geometry, and/or the sidewalls 1916 have a truncated triangular shape, or the 3D engineered structures comprise a pyramidal shape.
  • the device of examples 44-54 further comprising a UID layer 1910 below the MQW active region 1908, the UID layer 1910 comprising: a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN, or a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN.
  • the 3D engineered structures comprise core-shell nanostructures.
  • the core-shell nanostructures have a larger active region volume reduce the effective carrier density and efficiency droop.
  • the core-shell nanostructures are fabricated using the method of examples 21 or 22 to avoid direct Mg diffusion into the active QWs during the Mg diffusion process. 60.
  • the 3D engineered structures include an active region 1908 comprising InGaN/GaN or InGaN/InGaN QWs/QBs for visible emitters emitting visible light, or AlGaN/AlGaN QWS/QBs for ultraviolet emitters emitting ultraviolet electromagnetic radiation.
  • the device of examples 44-60 manufactured using the method of examples 2-43.
  • Advantages and Improvements of section III embodiments Section III of the present disclosure describes an LED structure, where the active QWs are p-type doped, with doping either in the QWs, the quantum barriers (QBs) separating the QWs, or both (with either uniform or localized, so-called delta doping).
  • the doping of QBs has the possible advantage of better QW material quality as doping is often associated with degraded materials performance in the regions with dopants.
  • LEDs or lasers with p-type doped MQWs have been well studied in the AlInGaAs material system due to their high modulation bandwidth 3–5 . This often comes with diminished threshold current and quasi unchanged turn-on voltage.
  • the advantages of the proposed LED structure designs include (i) low-droop GaN-based RGBY LEDs by volumetric hole injection, (ii) more design freedom for thick active regions with large number of QWs for high efficiency, (iii) improved efficiency of green LEDs and contribute to solve the green gap, (iv) may mitigate the size-dependent efficiency drop in micro-LEDs due to the reduced surface effects.
  • the position of the junctions within the MQWs (determined by the Mg diffusion length) can be adjusted by the duration and temperature of the Gallide process, to optimize uniformity of carrier injection. Due to the elimination of the need for hole transport in such structures, the associated transport delays between the wells are removed. Therefore, the design proposed here could significantly improve the modulation bandwidth of the LEDs, which is essential for visible-light communications.
  • the shape of the mesa structure can be designed so that the light emitted sideways is redirected by the metal contact to increase the source brightness.
  • An engineered large number of QWs for all wavelengths can be used in the active region without the issues with hole injections in the deeper wells.
  • white LEDs on a single wafer can be obtained by designing active RGBY QWs with different emission colors on a single structure on a single chip.
  • the white LED processed using this method has the advantage of higher efficiency compared to any phosphor-converted white LEDs (with slow and inefficient phosphor conversion process) and can be used in solid-state lighting as well as visible-light communications.

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Abstract

A light-emitting diode or laser including intentional V-defects and a planar hole waveguide. The active region includes a quantum well (QW) on or adjacent to a quantum barrier (QB). The planar hole waveguide comprises a barrier including (i) an alloy barrier (e.g., AlGaN, InAlN, or InAlGaN) interlayer in the QB or (ii) a delta doped layer at the interface between the QB and the QW, wherein the barrier enhances a hole lateral diffusion length that ensures or enables volumetric injection of holes into the active region. Also disclosed is a light emitting device, solar cell, or photodetector, comprising an array of three dimensionally (3D) engineered structures each comprising an active region comprising III-V material and a plurality of quantum wells and quantum barriers; and a vertical junction and a lateral junction with each of the 3D engineered structures. Holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction, and the quantum wells and/or the quantum barriers are p-type doped.

Description

METHODS OF HOLE INJECTION IN INDIUM ALUMINUM GALLIUM NITRIDE LIGHT-EMITTING DIODES CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C 119(e) of the following co- pending and commonly-assigned applications: U.S. Provisional Patent Application No.62/902,185, filed September 18, 2019, by James S. Speck, Morteza Monavarian, Claude C. A. Weisbuch, Cheyenne Lynsky, and Guillaume Lhereux, entitled “METHODS OF VOLUMETRIC HOLE INJECTION VIA INTENTIONAL V-DEFECTS IN INDIUM ALUMINUM GALLIUM NITRIDE LIGHT-EMITTING DIODES” Attorney’s Docket No. 30794.740-US-P1 (2020-058-1); U.S. Provisional Patent Application No.62/906,176, filed September 26, 2019, by James S. Speck, Morteza Monavarian, Claude C. A. Weisbuch, entitled “ENGINEERED THREE DIMENSIONAL CARRIER INJECTORS FOR INDIUM ALUMINUM GALLIUM NITRIDE DEVICES” Attorney’s Docket No.30794.741- US-P1 (2020-060-1); U.S. Provisional Patent Application No.62/925,965, filed October 25, 2019, by James S. Speck, Morteza Monavarian, Claude C. A. Weisbuch, entitled “ENHANCED HOLE INJECTION BY P-TYPE ACTIVE REGION AND LATERAL INJECTION IN InAIGaN LIGHT-EMITTING DEVICES” Attorney’s Docket No.30794.751-US-P1 (UC REF 2020-063-1); all of which applications are incorporated by reference herein STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This invention was made with Government support through Cooperative Agreement No. DE-EE0008204 from the United States Department of Energy. The Government has certain rights in this invention. BACKGROUND OF THE INVENTION 1. Field of the Invention. The present invention relates to light emitting diodes and lasers and methods of making the same. 2. Description of the Related Art. (Note: This application references a number of different references as indicated throughout the specification by one or more reference numbers in superscripts, e.g.,[x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein). Despite the extensive research efforts dedicated to GaN-based light-emitting diodes (LEDs) for solid-state lighting (SSL), a major challenge of LEDs, known as current droop, has not yet been resolved. Accordingly, those skilled in the art continue with research and development efforts in the field of increasing efficiency of optoelectronic devices. The present disclosure satisfies this need. SUMMARY OF THE INVENTION In a first embodiment, a light-emitting diode or laser including intentional V- defects and a planar hole waveguide is disclosed. The active region includes a quantum well (QW) on or adjacent to a quantum barrier (QB). The planar hole waveguide comprises a barrier including (i) an Aluminum Gallium Nitride (AlGaN) interlayer in the QB or (ii) a delta doped layer at the interface between the QB and the QW to enhance holes lateral diffusion length within the QBs prior to being captured by the QWs, which ensures or increases volumetric injection of holes into the active region. In a second embodiment, the present disclosure describes designs and geometries such as rectangular, pyramidal and triangular-ridge injectors to engineer the hole injection homogeneity and the efficiency droop in LEDs with different emission colors. In one or more examples, the designs involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation. A conformal p-GaN layer (using a novel Mg solid-state diffusion method and/or epitaxy) at the sidewalls of the formed structures can ensure or increase lateral hole injection in addition to the vertical injection. Therefore, volumetric hole injection can be obtained, which may in turn improve the efficiency droop through a reduction in carrier density for a given current density J. The present disclosure further describes a device (e.g., LED structure) where the active region is p-type doped, with doping either in the quantum wells (QWs), the quantum barriers (QBs), or both (with either uniform or delta doping). The doping of QBs having the possible advantage of better QW material quality as QW quality often degrades with doping. LEDs or lasers with p-type doped MQWs have been well studied in the AlInGaAs material system due to their high modulation bandwidth. In addition, this often comes with diminished threshold currents. If used in the usual geometry of contacting the extreme layers of the MQW layer stack, the usual issue of inhomogeneous hole injecting across the stack of QWs as in undoped MQW structures would occur. However, by applying a lateral p-GaN to p-type QWs, we inject all the stacked QWs simultaneously and with equal efficiencies. Novel LED designs described herein include the MQW active region fully or partially p-type doped surrounded by p-type lateral injectors to effectively make a p-type active region hole injector box. Locating the active QWs in the p-side of the junction eliminates the issue related to hole injection in conventional LEDs, where the active QWs are located in the unintentionally doped (UID) region of the junction (between p- and n- regions). The present disclosure describes the following device examples including, but not limited to, the following: 1. A device, comprising: a III-V light-emitting diode (LED) or III-V laser comprising intentional V- defects and a planar hole waveguide. 2. The device of example 1, wherein the III-V LED or III-V laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region. 3. The device example 2, wherein a thickness and composition of the alloy barrier interlayer forms a barrier suppressing transfer of the holes into the quantum wells, increasing hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer. 4. The device of example 2, wherein one or more of the repeat units comprise another alloy barrier interlayer on another side of the QB to improve waveguiding of the holes. 5. The device of example 1, wherein the LED or laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises a delta-doped layer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region. 6. The device of example 5, wherein: the delta-doped layer comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of holes into the QW, leading to a longer lateral diffusion of the holes in QBs before being captured by the QWs. 7. The device of example 5, wherein one or more of the repeat units include another delta-doped layer on another side of the QB to improve waveguiding of the holes. 8. The device of any of the examples 5-6, wherein the delta doped layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer. 9. The device of any of the preceding examples 1-8, further comprising: the active region comprising multi quantum wells, an n-type layer for providing electrons to the active region; and an unintentionally doped or n-type doped AlGaN layer between the n-type layer and the active region. 10. The device of any of the examples 1-9, wherein the V-defects comprise V-shaped lateral injectors comprising a superlattice structure coupled to the quantum wells in the active region. 11. The device of example 10, wherein the V-shaped lateral injectors comprise V-shaped features on a patterned dielectric or a metal mask. 12. The device of any of the examples 1-11, wherein the LED or laser comprises a III-nitride LED or III-nitride laser. 13. A device, comprising: an array of three dimensionally (3D) engineered structures each comprising an active region comprising III-V material and a plurality of quantum wells; and a vertical junction and a lateral junction with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction. 14. The device of example 13, further comprising a p-type layer on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region. 15. The device of example 13, further comprising: an n-type III-V layer providing electrons to the quantum wells; a p-type layer on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the quantum wells on the sidewall so as to inject holes laterally into each of the quantum wells; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer and the 3D engineered structures. 16. The device of example 15, wherein the p-type layer comprises p-type dopants diffused from a dopant layer deposited on the p-type layer. 17. The device of example 15, wherein the III-V layer comprises GaN, the p-type layer comprises p-type GaN, the dopant layer comprises a Magnesium layer, and the p-type dopants comprise Magnesium. 18. The device of any of the examples 13-17, further comprising a hole blocking barrier layer between the n-type layer and the active region so as to prevent or reduce direct hole injection to the n-side of the junction with the active region. 19. The device of example 18, wherein the hole blocking layer comprises AlGaN, InAlN, or InAlGaN. 20. The device of example 18, wherein the hole blocking layer comprises an n-type delta doped III-V layer. 21. The device of any of the examples 13-20, wherein the device comprises a laser or light emitting diode and the III-V material and III-V layer comprise III-nitride. 22. The device of any of the examples 14-21, wherein the sidewalls: are inclined at an angle of less than 45 degrees, or at an angle between 45 degrees and 60 degrees, with respect to a base of the 3D engineered structures so as to increase surface area contact of the quantum wells with the p-type layer. 23. The device of any of the examples 13-22, wherein the 3D engineered structures have the sidewalls forming a convex or concave geometry. 24. The device of any of the examples 13-23, wherein the sidewalls have a truncated triangular shape, or the 3D engineered structures comprise a pyramidal shape. 25. The device of any of the examples 13-24, wherein the active region comprises a plurality of QWs and QBs and the QWs and/or the QBs are p-type doped. 26. The device of any of the examples 13-25, further comprising an unintentionally doped (UID) layer below the active region comprising multi quantum wells, the UID layer comprising: a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN, or a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN. 27. The device of any of the examples 25-26, wherein the QBs comprise delta doping or modulation doping. 28. The device of any of the examples 13-27, wherein the 3D engineered structures comprise core-shell nanostructures. 29. The device of example 28, wherein the core-shell nanostructures have a larger active region volume so as to reduce an effective carrier density and efficiency droop. 30. The device of any of the preceding examples 1-29, wherein the device comprises a hetero- and/or homo-junction GaN-based nano laser or LED for photonics and/or nanometrology applications. 31. The device of any of the examples 1-30, wherein the device comprises a nanolaser or nano LED comprises a III-nitride nanowire LED or a nanowire laser useful as a building block in a photonic integrated circuits (PIC) or as a light source. 32. The device of any of the examples 13-31, wherein the device is a light emitting device, a solar cell, a detector, or a transistor. 33. The device of any of the examples 1-27, wherein the device comprises a planar or a core shell structure, the core shell comprising the p-type layer forming a shell on a core comprising the active region, the device formed using a top-down or bottom-up geometry. 34. The device of one or more of the preceding examples 13-33, wherein the device comprises a transistor useful in a power electronics application. 35. A device useful in a power electronics application, comprising: an array of three dimensionally (3D) engineered structures each comprising III-V material and a p-n junction between a p-type layer and an n-type layer; the p-n junction comprising a vertical junction and a lateral junction, wherein holes are injected through the vertical junction and the lateral junction. DETAILED DESCRIPTION OF THE INVENTION In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings in which like reference numbers represent corresponding parts throughout: Figure 1. (a) Schematic of a typical planar LED structure for vertical injection, comprising top and bottom injecting GaN layers of n- or p- type respectively, and an active multi-quantum well (MQW) region, made of alternate InGaN (quantum wells or QWs) and GaN (quantum barriers or QBs) layers, with (b) band profile 1 along cut ^. In addition, LEDs often include a p- type AlGaN barrier before the top p-doped GaN layer. Due to the large polarization barrier to hole transport in the vertical direction, holes are typically injected only into the top QWs near the p-side. Therefore, the QWs near the p-GaN mainly contribute to the recombination and emission. Note that the electrons are normally injected homogeneously across all the QWs. In this planar structure, electrons and holes are homogeneously distributed in the QW planes (neglecting alloy disorder effects). Figure 2. (a) Cross-sectional and (b) top-view schematics of a V-defect in a MQW LED structure. Figure 3. Schematics of a portion of LED active region with a V-defect with limited in-plane lateral hole injection from the V-defect, injection region indicated by the blue rectangle, into all QWs. Cuts
Figure imgf000011_0001
correspond to band diagrams 2, 3, 4, and 5, respectively. Hole injection into the barriers through sidewalls into QWs and QBs are shown in cuts
Figure imgf000011_0002
(c) respectively. Due to the thin QWs and small electric fields of semipolar {10-11} planes, holes are easily injected in the QWs and QBs next to the V-defect. Cut
Figure imgf000011_0003
(d) shows three types of hole injection pathways in proximity to the V-defect sidewall: the first, from the top p-layer, mainly in the top QW; the second and third, quasi-homogeneous for all QWs and QBs edges near the V-defect, from holes injected in the QWs and QBs. However, moving away from the edge of the V-defect sidewall (cut
Figure imgf000011_0004
(e)) the hole population originating from QWs or barrier injection through the V-defect sidewalls has decayed due to the short lateral hole diffusion length in the QWs and QBs. Forward voltage is diminished by the small barriers (absence of polarization fields, thinner barriers), however, the impact on droop is limited by the short lateral hole diffusion length, therefore not solving the inhomogeneous injection problem of hole injection from the top layer. Note that the electrons are being injected from the n-doped bottom injecting layer of the structure in cuts
Figure imgf000011_0005
Figure 4. (a) Schematic of a portion of LED active region with V-shaped lateral injectors and engineered QBs. Cut
Figure imgf000011_0006
corresponds to band diagram 6 with (b) AlGaN or (c) Si d-doped planar hole waveguide (PHW) structures to maintaining injected holes in the QBs for long range lateral hole diffusion. With PHWs, holes are expected to diffuse half the length of the V-injector spacing. Band diagrams in cut
Figure imgf000012_0001
shows homogeneous hole injection from the QBs to the QWs throughout the V- injector, indicating long-range hole injection in all QWs using PHW structures. Note that the electrons are being injected from the n-side of the structure in cut
Figure imgf000012_0002
and they can propagate through the AlGaN layer in (b) or Si į-doped layer in (c) by thermionic emission or tunneling to the QWs. An additional feature could be a thicker AlGaN or d-doped barrier on the n-side of the active region to prevent or reduce direct hole injection in the n-layer, which would be detrimental to QW injection (Figure 5). Figure 5. (a) Spurious direct injection of holes into n-layer; to avoid this, (b) the first layer below the first QW could be an unintentionally doped or n-type doped AlGaN layer of sufficient thickness or a Si į-doped layer of sufficient doping level and thickness to play the role of a blocking barrier to hole transport directly to the n- side. Figure 6(a). Cross-sectional schematic of a final processed LED device structure that incorporates V-shaped lateral injectors (VLIs) and planar hole waveguides (PHWs). Figures 6(b) and 6(c). Flowcharts illustrating methods of making a device. Figure 7. (a) Cross-sectional and (b) top-view schematics of a V-defect in a MQW LED structure. Figure 8. Schematic of a V-defect MQW LED structure with vertical and lateral hole injections (a) without and (b) with a blocking barrier layer (either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer) to prevent or reduce direct hole injection to the n-side of the junction. The structure in (b) may reduce the current leakage in V-defect LEDs. Figure 9. (a,b) Cross-sectional and (c,d) top-view schematics of active region configurations for (a) rectangular injectors and (b,c,d) V-injectors in (c) pyramidal and (d) triangular-ridge geometries. Figure 10. Cross-sectional SEM images of GaN samples etched using (a) dry etching and (b) dry etching plus wet etching using TMAH. The images show the possibility of obtaining different trench geometries (triangular and rectangular) with the combination of dry and wet etching processes. Figure 11. Mg diffusion process flow: (a) unintentionally doped (UID) or lightly doped GaN growth, (b) deposition of Mg layer and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ^C to 1000 ^C), (f) removal of the metal and Gallide from the surface. Figure 12. Schematics of a simplified pyramidal structure after (a) Mg diffusion, and followed by (b) short and (c) long MOCVD or MBE grown p-GaN to achieve coalescence, i.e. planarized overgrowth over the pyramids. The coalesced structures may lead to an easier post-growth device fabrication process while may slightly increase the p-type resistance due to a thicker p-GaN. Figure 13. Schematic representation of hole injection from the top and the sidewall p-GaN of a 3D engineered hole injector into the active regions and into the n-GaN in (a) basic structure, (b) structure with shorter sidewall p-GaN, and (c) structure with underlying blocking barrier layer (either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta- doped layer). Insets show zoomed-in images to more clearly indicate the changes in the structures. Structures (b) and (c) could avoid direct injection of holes from the sidewalls to the n-GaN. The length of the p-GaN sidewalls, the thickness and composition of the alloy barrier layer or thickness and doping level of the n-type delta doped layer could be designed to effectively block the holes but not limiting the electron transport and injection to the p-side. Similar methods can be applied to other geometries shown in Figure 9. Figure 14. Cross-sectional schematic of an approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process: (a) active region growth, (b) mesa etch, (c) dielectric mask for regrowth, (d) regrowth of 3D UID layer, (e) deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 11, and (f) formation of the 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and Gallide layers. Note that the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction. Figure 15. Cross-sectional schematics of fully processed LEDs with engineered (a) triangular and (b) rectangular hole injector designs. Note that the p- side of the LED junctions can be made using Mg diffusion to the InGaN/GaN MQW structures or a regrown UID GaN layer, as shown in Figure 14. The structures shown here utilizes both shorter sidewall p-GaN and underlying blocking barrier layer (either an alloy barrier layer such as AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer) to eliminate any leakage associated with direct hole injection from the sidewall p-GaN to the n-side of the junction. Note that, the length of the p-GaN sidewalls, the thickness and composition of the alloy barrier layer or thickness and doping level of the n-type delta doped layer could be designed to effectively block the holes but not limiting the electron transport and injection to the p-side. Figure 15(c). Flowchart illustrating a method of making a device. Figure 16. Cross-sectional schematics of nanostructure-based LED structures with (a) planar and (b) core-shell QWs/QBs using top-down and bottom-up approaches. In both cases, the p-GaN can be uniformly formed using Mg solid state diffusion described in Figure 5 and throughout this invention. The core-shell geometry shown in (b) has an additional advantage of ultra-large active region volume, which can further reduce the effective carrier density and efficiency droop. Figure 17. Cross-sectional schematic of an approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process for a bottom-up core- shell nanostructure geometry: (a) core-shell active region growth, (b) core-shell regrowth of a UID layer, (c) conformal deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 11, and (d) formation of a core-shell 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and Gallide layers. Note that the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction. To avoid direct Mg diffusion into the active QWs during the Mg diffusion process in nanostructure geometries shown in Figure 16 (a), a similar approach can be applied, which would be similar to the method described in Figure 14. Figure 18. Cross-sectional schematic of a process to fabricate fully lateral p-n junctions including (a) n-GaN growth, (b) mesa isolation etch, (c) dielectric deposition, (d) conformal deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 11, (e) formation of a p-GaN column by Mg diffusion method followed by removal of the metal and Gallide layer, and (f) conformal deposition of the p- and n-contacts. The widths of the p-GaN and n-GaN are arbitrary in this method, which provides a platform for p-n junctions with extreme dimensions which are not normally possible by vertical designs. For example, extremely wide drift regions are possible in this design which can provide very large reverse blocking voltages for power electronic applications. Figure 19. Cross-sectional schematic of a (a) standard planar MQW LED with UID active region and (b) LED with a design according to the present invention comprising p-type doped active region and lateral hole injection. Note that the QBs are p-type doped in (b) but due to the modulation doping, the QWs become p-type active, as indicated by the arrows. Figure 20. Schematics of hole injection in standard planar vertical MQW LED with (a) UID active region, (b) p-type active region, and (c) LED with a p-type active region and a lateral injector design as described in the present invention. Figure 21. Vertical band diagram schematics of LED design with (a) UID MQW active region and (b) p-type MQWs active region according to the present invention. Note that the holes are abundant in the QWs in the design in (b) and electrons would easily pass the junction and recombine in the QWs in forward bias. Figure 22. Schematics of an active region consisting of QWs and QBs with the QBs being doped by Mg using (a) uniform doping and (b) delta doping. Figure 23. Cross-sectional SEM images of GaN samples etched using (a) dry etching and (b) dry etching plus wet etching using Tetramethylammonium hydroxide (TMAH). The images show the possibility of obtaining different trench geometries (triangular and rectangular) with the combination of dry and wet etching processes. Figure 24. Mg diffusion process flow: (a) UID or lightly doped GaN growth, (b) deposition of Mg layer or Mg compound layer such as MgF2 and Pd or Pt, (c,d,e) Mg diffusion and Gallide formation at elevated temperatures (800 ^C to 1000 ^C), (f) removal of the metal and Gallide from the surface. Figure 26. Cross-sectional schematic representation of a method to avoid direct hole injection from p-GaN sidewalls to the n-GaN by a conformal dielectric passivation prior to Mg diffusion: (a) active region growth, (b) mesa etch and conformal dielectric deposition, (c) deposition of Mg layer and metal layer required for the Mg diffusion process as described in Figure 6, and (d) formation of the 3D p- GaN over the active region by Mg diffusion method followed by removal of the metal and gallide layers. Figure 26. Cross-sectional schematic of a few different designs for the geometry of the p-type active region, the mesa etch depth and using underlying layer to avoid direct hole injections into the n-side of the junction. (a) deep etch but long p- GaN sidewalls, (b) deep etch and p-GaN sidewall length being exactly at the bottom of the first QW, (c) deep etch but short p-GaN sidewalls, (d) shallow etch and longest possible p-GaN sidewalls, (e) deep etch and short p-GaN sidewalls with a blocking barrier layer (either an AlN, AlGaN, InAlN, or InAlGaN barrier layer or an n-type Si delta doped layer) and (f) shallow etch with a blocking barrier layer (either an AlN, AlGaN, InAlN, or InAlGaN barrier layer or an n-type delta doped layer). The shallow etch depth above the first QW (nearest to the n-side of the junction) prevents or reduces direct injection of holes to the n-region. Controlling of the length of the p- GaN sidewall (a-c) can also be considered as it will have similar effects on the leakage as the mesa etch depth control. Also, the blocking barrier layer in (e) and (f) would serve as a hole blocking layer to avoid direct injection of holes to the n-side of the junction and to avoid current leakage. Figure 27. Cross-sectional schematic of an approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process: (a) active region growth, (b) mesa etch, (c) dielectric mask for regrowth, (d) regrowth of 3D UID layer, (e) deposition of Mg layer (or Mg compound layer such as MgF2) and metal layer required for the Mg diffusion process as described in Figure 6, and (f) formation of the 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and gallide layers. Note that the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction. Figure 28. Cross-sectional schematics of the processed LED structures with p- type active region and conformal Mg diffused p-GaN with (a) triangular and (b) rectangular geometries. Note that this is to demonstrate a building block of the LEDs and designs with arrays of such structures can be processed as well. The number of QWs can be large in this design as shown in this figure. Figure 29. Flowchart illustrating a method of making a device. DETAILED DESCRIPTION OF THE INVENTION In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Technical Description Nomenclature GaN and its ternary and quaternary compounds incorporating aluminum and indium (AlGaN, InGaN, AlInGaN) are commonly referred to using the terms (Al,Ga,In)N, III-nitride, III-N, Group III-nitride, nitride, Group III-N, Al(1-x-y)InyGaxN where 0 < x < 1 and 0 < y < 1, or AlInGaN, as used herein. All these terms are intended to be equivalent and broadly construed to include respective nitrides of the single species, Al, Ga, and In, as well as binary, ternary and quaternary compositions of such Group III metal species. Accordingly, these terms comprehend the compounds AlN, GaN, and InN, as well as the ternary compounds AlGaN, GaInN, and AlInN, and the quaternary compound AlGaInN, as species included in such nomenclature. When two or more of the (Ga, Al, In) component species are present, all possible compositions, including stoichiometric proportions as well as “off- stoichiometric” proportions (with respect to the relative mole fractions present of each of the (Ga, Al, In) component species that are present in the composition), can be employed within the broad scope of the invention. Accordingly, it will be appreciated that the discussion of the invention hereinafter in primary reference to GaN materials is applicable to the formation of various other (Al, Ga, In)N material species. Further, (Al,Ga,In)N materials within the scope of the invention may further include minor quantities of dopants and/or other impurity or inclusional materials. Boron (B) may also be included. Similarly III-V materials or devices are equivalent and broadly construed to include respective compounds or compositions comprising Group III and Group V species, e.g., but not limited to, binary, ternary and quaternary compositions of such Group III species combined with Group V species, where Group III, III, Group V, V refer to groups in the periodic table of the elements. One approach to eliminating the spontaneous and piezoelectric polarization effects in GaN or III-nitride based optoelectronic devices is to grow the III-nitride devices on nonpolar planes of the crystal. Such planes contain equal numbers of Ga (or group III atoms) and N atoms and are charge-neutral. Furthermore, subsequent nonpolar layers are equivalent to one another so the bulk crystal will not be polarized along the growth direction. Two such families of symmetry-equivalent nonpolar planes in GaN are the {11-20} family, known collectively as a-planes, and the {1- 100} family, known collectively as m-planes. Thus, nonpolar III-nitride is grown along a direction perpendicular to the (0001) c-axis of the III-nitride crystal. Another approach to reducing polarization effects in (Ga,Al,In,B)N devices is to grow the devices on semi-polar planes of the crystal. The term “semi-polar plane” (also referred to as “semipolar plane”) can be used to refer to any plane that cannot be classified as c-plane, a-plane, or m-plane. In crystallographic terms, a semi-polar plane may include any plane that has at least two nonzero h, i, or k Miller indices and a nonzero l Miller index. Some commonly observed examples of semi-polar planes include the (11-22), (10-11), and (10-13) planes. Other examples of semi-polar planes in the wurtzite crystal structure include, but are not limited to, (10-12), (20-21), and (10-14). The nitride crystal’s polarization vector lies neither within such planes or normal to such planes, but rather lies at some angle inclined relative to the plane’s surface normal. For example, the (10-11) and (10-13) planes are at 62.98° and 32.06° to the c-plane, respectively. I. Methods of volumetric hole injection via intentional v-defects in indium aluminum gallium nitride light-emitting diodes Current droop refers to the reduction in the efficiency of GaN-based LEDs at high injection levels1. Auger non-radiative recombination has recently been revealed to be the origin of the current droop2, as it increases faster than the radiative emission rate with carrier densities. Since the Auger rate is strongly dependent on carrier densities (n and p for electrons and holes, respectively), one way to reduce the Auger rate and thus current droop is by reducing n and/or p for an injected current density (J). To reduce the Auger recombination rate, a straightforward approach is to reduce n and/or p by increasing the active region volume. Many optimized LED designs incorporate multi-quantum well (MQW) active regions, hoping to reduce the carrier density per quantum well (QW) at a given J. However, as shown in Figure 1, the hole injection in such structures is very inhomogeneous and only the top QWs are populated by holes (in the remainder of this description, we call top QWs, the QWs that are grown nearest to the p-GaN layer, as the growth sequence of a basic LED structure is n-GaN followed by QWs followed by p-GaN). Compared to electrons, holes have poor vertical transport properties, which prevents them from reaching down to the deeper QWs near the n-side of the junction. In longer wavelength LEDs (green, yellow and red LEDs) the situation gets worse due to the higher polarization- related energy barrier to hole transport. The limitation of hole transport leads to a very inhomogeneous current injection. The top QWs receiving most of the hole current (Figure 1) have large joint electron and hole carrier densities and hence large Auger non-radiative recombination, leading to significant droop. This effect is largely independent of the number of QWs, as most QWs are inactive for light emission due to the lack of holes. Hence, methods of carrier injection in the whole active volume, called hereafter volumetric carrier injection, are of substantial interest as they would lead to low-droop GaN-based LEDs emitting at any wavelengths. V-shaped defects (commonly referred to as V-defects) have recently improved the efficiency of LEDs, particularly in the yellow and green wavelengths3 by diminishing their forward voltage and hence improving their wall-plug efficiency. Schematics of a V-defect in a multi-QW LED structure are shown in Figure 2. Intentional V-defects, which we refer to as “V-shaped lateral injectors” (VLIs), can be engineered by controlled nucleation below the MQW stack and can have engineered semipolar sidewall {10-11} QWs (or possibly no sidewall QWs). The characteristic dimensions of V-defects (lateral size, depth, density) can be controlled by growth conditions4. Since the sidewall QWs, if present, are typically thin, have low In content, and are on {10-11} semipolar planes with a small polarization discontinuity between InGaN and GaN5, they present a small barrier for hole injection (Figure 3), hence reducing the LED forward voltage. An early 3D simulation for blue V-defect-based LEDs has been performed6. The improvement is attributed to the lateral hole injection obtained at the recombination plane of the V-defect, simultaneously in all QWs of the active region. However, no or marginal improvement was seen on efficiency droop, due to the small volume laterally injected from the injection region in the V-defect (Figure 3). Holes directly injected in the InGaN QWs have very small lateral diffusion lengths due to the drift field in the quantum barrier (QB) which forces holes to drift to the QWs with no barrier for capture into the QWs. Due to the band-bending between the QWs and the QBs, the laterally injected holes in the QBs would be immediately captured by the QWs at the edge of the V-defect (Figure 3) and recombine. Hence, the lateral hole injection in a V-shaped defect, whether injected in the QWs or QBs, is still very concentrated in a small fraction of the QWs area and thus does not strongly improve hole injection in the whole area of lower QWs, and therefore the efficiency droop is hardly changed. The difference with usual planar structures is that, instead of having holes injected preferentially in the QW proximal to the p-layer, holes are injected in every QW but only on a small fraction of their area (Figure 3). An engineered structure is then necessary to optimize lateral hole injection to increase or ensure volumetric injection and reduce the efficiency droop in all wavelengths. The hole diffusion length in the QWs cannot be improved readily as it is determined by electron-hole recombination. However, we can increase the hole diffusion length in the QBs as it is not seriously limited by recombination because the local electron density in the QBs is low due to the barrier height. The hole diffusion length is thus determined by the downfall of holes into the adjacent QW (Figure 4). Here, we propose an engineered planar hole waveguide (PHW) design to enhance the laterally injected minority hole diffusion length in the QBs (Figure 4) by introducing (i) thin AlGaN interlayers or (ii) thin Si-delta doped GaN layers near or just below each of the QWs. In the case of AlGaN interlayer, the thickness and composition of the AlGaN layer is engineered to ensure or increase long range hole diffusion in the QBs before holes are captured by the QWs via tunneling or percolative transport through the disordered AlGaN layer (Figure 4(b)). In the case of Si delta-doped GaN layer, the band-bending associated with the high doping at the QW/QB interface provides a barrier to the hole injection, leading to longer lateral diffusion of the holes in QBs before being captured by the QWs (Figure 4(c)). The doping level of the Si-doped GaN layer and the exact position in the QBs with respect to the QWs are design considerations. Note that the introduced Si delta doping would have negligible effects on the sidewall doping as the sidewall semipolar {10-11} planes have significantly lower Si incorporation compared to c-plane. In order to improve the hole injection in the QBs relative to the direct hole injection in the QWs, the QBs can be made of InGaN which will lower the injection barrier from the p- type injection layer. The lower barriers can be made of homogeneous InGaN material, graded InGaN material, quaternary materials of the InGaAlN materials family, or a superlattice made of the InGaAlN materials family. The thickness of QBs with respect to the thickness of QWs can also be designed to increase the total volume of the QBs and to improve the hole injection in the QBs relative to the direct hole injection in the QWs. The QBs can also be modulation doped by Mg delta doping to reduce the injection barrier in the QBs to improve the hole injection in the QBs relative to the direct hole injection in the QWs. Figure 4 shows the band diagrams for LEDs with VLIs, and with VLIs plus PHWs. The concept is to induce long-range lateral transport of minority holes injected into engineered QBs to ensure or increase volumetric injection. Here, by volumetric hole injection, the proposed design would significantly reduce the local p in active QWs for a given total J and thus lead to droop reduction. Realization of lateral diffusion lengths on the order of half of the V-defect spacing would enable nearly uniform hole injection of all QWs in the MQW stack and thus a viable solution to minimizing droop in a MQW active layer. An active region with large number of QWs can be used to maximize the active volume, thanks to the homogeneous lateral hole injection allowed by using the VLIs plus PHW structures. The optimized QW number is decided by the depth of the V-defect, the optimal thicknesses of the QWs and QBs, so as to obtain uniform injection of both electrons and holes. Also, care should be taken to prevent or reduce direct hole injection in the n- layer, which would compete with hole injection into the QWs (Figure 5). To avoid this, the first layer below the first QW could be an unintentionally doped or n-type doped AlGaN layer of sufficient thickness to play the role of a blocking barrier to hole transport directly into the n-side. A Si delta-doped layer of sufficient doping level and thickness can also be used to serve as blocking barrier to hole transport directly into the n-side. There are many growth conditions which lead to V-pit formation, most often around dislocations. These have been shown to act as lateral injectors3. Preferred ways of obtaining shape- and density-controlled V-shaped lateral injectors can include, but are not limited to, using (i) pre-active region InGaN/GaN superlattice stacks or (ii) ex-situ dielectric or metal mask using high-resolution imprint/lithography followed by metal-organic chemical vapor deposition (MOCVD). For the superlattice approach, thickness, composition, and growth conditions of the stack are design parameters. For the ex-situ mask and growth approach, various mask patterns, including circles and stripes with different openings and pitch sizes can be applied. For the stripe patterns, various orientations of stripes can be used. Intentionally high density of VLIs followed by PHW approach can significantly mitigate the droop in all wavelengths. The structure can be grown using an industrially viable MOCVD technique. Figure 6 shows a schematic of a fully processed LED with VLIs and PHWs. The advantages of these LED structure designs include (i) reduced droop by reduction of p in the active region, (ii) improved spatial uniformity of the emission due to the more uniform hole injection, (iii) industrial compatibility, and (iv) ease of implementation. Additional design parameters include: the relative thicknesses of QWs and QBs, the composition and thickness of the AlGaN layer, the doping and position of Si delta- doped layers, the eventual addition of another AlGaN and/or delta Si-doped GaN layer on the other side of each QB to improve hole waveguiding, and the density and geometry of VLIs. This method can be applied to all wavelengths by changing the active region bandgap. White light can also be generated on a single LED on a single chip using stacks of red-green-blue-yellow (RGBY) QWs in a single LED on a single chip. The white LEDs developed using this technique would provide higher efficiency and higher modulation bandwidths compared to the conventional phosphor converted blue LEDs (which rely on phosphor conversion which is a very inefficient and slow process) for solid-state lighting and visible-light communication. This injection method can be similarly applied to other III-nitride light emitting structures such as UV LEDs and lasers. The method can be applied to light emitting structures with different crystal orientations. Example Embodiments 1. A III-nitride light-emitting diode comprising intentional V-defect formation and a planar hole waveguide and method of making the same. 2. The method of embodiment 1, using substrates with polar c-plane, either Ga-face or N-face, and/or nonpolar and/or semipolar orientations. 3. Growth of the V-defect LED including the planar hole waveguide by metalorganic chemical vapor deposition. 4. Applying engineered thin AlGaN interlayers in the QBs right below the QWs to enhance hole lateral diffusion length to ensure or increase volumetric injection. 5. Addition of another AlGaN layer on the other side of each QB to improve hole waveguiding. 6. Applying an engineered Si delta-doped GaN layer in the QBs just below the QWs to enhance hole lateral diffusion length to ensure or increase volumetric injection. 7. Addition of another Si delta-doped GaN layer on the other side of each QB to improve hole waveguiding. 8. Addition of an unintentionally doped or n-type doped AlGaN layer above the n layer below the active MQW region. 9. Formation of intentional V-shaped lateral injectors using pre-QW superlattice structures. 10. Formation of intentional V-shaped lateral injectors using a patterned dielectric or metal mask followed by growth of V-shaped features to control size and density of V-shape lateral injectors. 11. In embodiment 10, different patterns including circles and stripes with different opening and pitch sizes and stripe orientations can be used. 12. Different densities of V-shaped lateral injectors can be used to further enhance the hole lateral injection. 13. An engineered large number of QWs for very high active region volume to enhance efficiency and reduce droop. 14. The method can be applied to all wavelengths by changing the active region bandgap. 15. Method of white light generation using stacks of RGBY QWs in a single LED on a single chip by stacking QWs emitting at different wavelengths, wherein the stack is laterally injected. 16. The method can be applied to other III-V material systems. 17. The method can be applied to other structures such as UV LEDs and lasers. 18. In various examples, the PHW comprises a delta doped layer and/or an alloy barriers having a doping and/or alloy composition suitable for waveguiding the holes. Further Device and Method Examples 1. Figure 6(a)-6(b) illustrate a method of making a device 600, comprising: growing a III-V light-emitting diode (LED) 602 or III-V laser comprising intentional V-defects (VLI) and a planar hole waveguide (PHW). 2. The method of example 1, further comprising growing the III-V LED or III-V laser on a substrate 604 having a polar c-plane, either Ga-face or N-face, a nonpolar, and/or a semipolar orientation. 3. The method of any of the preceding examples, further comprising growing the III-V LED or III-V laser, including the V-defects and the planar hole waveguide, by metalorganic chemical vapor deposition. 4. Figure 5 and Figure 6(a)-6(b) illustrate the method of any of the previous examples, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide comprising an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 5. The method of example 4, further comprising growing a thickness and a composition of the alloy barrier interlayer so as to form a barrier suppressing transfer of the holes into the QWs, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer. 6. The method of example 4 or 5, further comprising, in one or more of the repeat units, another alloy barrier layer on the other side of the QB to improve waveguiding of the holes. 7. The method of examples 4-6, wherein the alloy barrier comprises AlGaN or InAlN or InAlGaN. 8. Figure 5 and 6(a)-6(b) illustrate the method of examples 1-7, wherein the growing comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide comprising a delta-doped III-V layer 610 in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 9. The method of example 8, wherein: the delta-doped layer 610 comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of the holes into the QW, the barrier increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling through the doping layer. 10. The method of example 9, further comprising growing, in one or more of the repeat units, another delta-doped III-V layer on the other side of the QB to improve waveguiding of the holes. 11. The method of examples 8-10, wherein the delta doped III-V layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer. 12. Figure 6(a)-6(b) illustrates the method of any of the preceding examples, wherein the growing comprises: growing the active region 606 comprising multi quantum wells, growing an n-type layer 608 for providing electrons to the active region; and growing an unintentionally doped or n-type doped AlGaN layer 608 between the n-type layer and the active region. 13. The method of any of preceding examples, further comprising forming intentional V-shaped lateral injectors (VLI) using a superlattice structure grown prior to the quantum wells in the active region. 14. Figure 6(b) illustrates the method of any of the preceding examples, further comprising: forming intentional V-shaped lateral injectors (VLI) using a patterned dielectric or metal mask, as illustrated in block 650; after forming the V-shaped lateral injectors, optionally growing V-shaped features on the patterned dielectric mask so as to control a size and density of the V- shaped lateral injectors (as illustrated in Block 652); and growing the III-nitride LED or III-V laser on the V-shaped lateral injectors, as illustrated in block 654. 15. The method of example 14, wherein dielectric or metal mask includes a pattern comprising circles and/or stripes, the method further comprising selecting a pitch, dimensions, and an orientation of the circles and/or stripes. 16. The method of examples 14 or 15, further comprising selecting a density of the V-shaped lateral injectors so as to enhance or tailor the lateral injection of the holes into the active region. 17. The method of any of the preceding examples, further comprising selecting a larger number of quantum wells in the active region of the LED or laser so as to increase a volume of the active region and enhance or tailor efficiency and reduce current droop of the LED or laser. 18. The method of any of the preceding examples, further comprising selecting the composition of the active region so as to obtain the LED or laser emitting electromagnetic radiation having any visible wavelength. 19. Figure 5 and Figure 6(a) illustrates the method of any of the preceding examples, further comprising: growing the active region 604 of the LED or laser comprising a stack of quantum wells (QW), each of the quantum wells configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength; and wherein the stack is laterally injected with holes. 20. The method of any of the preceding examples, wherein the LED or laser comprises a III-nitride LED or III-nitride laser. 21. The method of any of the preceding examples, wherein the LED or laser emits ultraviolet light. 22. Figure 6(a) illustrates a device 600, comprising: a III-V light-emitting diode (LED) 602 or III-V laser comprising intentional V-defects (VLI) and a planar hole waveguide (PHW) (e.g., V-defects on or above, connected to, or coupled to, the planar hole waveguide). 23. Figure 6(a) further illustrates the device of example 22, wherein the III-V LED or III-V laser comprises: an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 24. The device example 23, wherein a thickness and composition of the alloy barrier interlayer forms a barrier suppressing transfer of the holes into the quantum wells, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer. 25. The device of example 23 or 24, wherein one or more of the repeat units comprise another alloy barrier interlayer on the other side of the QB to improve waveguiding of the holes. 26. The device of example 22, wherein the LED or laser comprises: an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises a delta-doped layer 610 in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 27. The device of example 26, wherein: the delta-doped layer comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of holes into the QW, leading to a longer lateral diffusion of the holes in QBs before being captured by the QWs. 28. The device of example 26, wherein one or more of the repeat units include another delta-doped layer on the other side of the QB to improve waveguiding of the holes. 29. The device of any of the examples 26-28, wherein the delta doped layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer. 30. The device of any of the preceding examples 22-29, further comprising: an active region 606 comprising multi quantum wells, an n-type layer 608 for providing electrons to the active region; and an unintentionally doped or n-type doped AlGaN layer 610 between the n-type layer and the active region. 31. The device of any of the examples 22-30, further comprising intentional V-shaped lateral injectors VLI comprising a superlattice structure coupled to quantum wells in the active region. 32. The device of example 31, wherein the V-shaped lateral injectors comprise V-shaped features on a patterned dielectric or metal mask. 33. The device of any of the examples 22-32, wherein the LED or laser comprises a III-nitride LED or laser. 34. The device or method of any of the preceding examples, wherein the holes recombine with electrons in the active region or quantum well so as to emit electromagnetic radiation comprising visible, infrared, or ultraviolet wavelengths. 35. Figure 6(c) and 6(a) illustrate the method or device of any of the previous examples, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide PHW comprising a III-nitride interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region, wherein: a composition and thickness of the III-nitride interlayer is selected to form a barrier suppressing transfer of the holes into the QWs, increasing the hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the AlGaN layer. 36. The device or method of any of the preceding examples, wherein: the active region comprises quantum wells (QWs) having quantum barriers (QBs) confining electrons and holes in the quantum wells, and the QBs comprise InGaN so as to reduce a barrier between the QB and a p- type injection layer, wherein the barrier comprises a barrier for holes being injected from the p-type layer to the QB. 37. The device or method of example 36, wherein the InGaN comprises homogeneous InGaN material, graded InGaN material, quaternary materials of the InGaAlN materials family, or a superlattice including InGaAlN. 38. The device or method of examples 35-37, wherein a thickness of the QBs with respect to a thickness of QWs is designed to increase a total volume of the QBs and to increase injection of the holes into the QBs relative to a direct injection of the holes into the QWs. 39. The device or method of examples 35-38, wherein the QBs are modulation doped by Mg delta doping to: reduce the barrier for the holes being injected into the QBs from the p-type injection layer, and increase injection of the holes into the QBs relative to a direct injection of the holes into the QWs. 40. The device or method of any of the preceding examples 1-39, further comprising a hole blocking layer 610 between a first quantum well in the active region and an n-type layer providing electrons to the active region. 41. The device or method of example 40, wherein the hole blocking layer comprises an unintentionally doped or n-type doped AlGaN layer of sufficient thickness, or an Si delta-doped layer of sufficient doping level and thickness. 42. Figure 6(a) and block 656 of Figure 6(c) illustrate the method or device of any of the previous examples 1-41, wherein growing the III-V LED or III-V laser comprises: growing an active region 606 including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, growing the planar hole waveguide PHW comprising: an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region and/or a delta-doped III-V layer in the QB to enhance a hole lateral diffusion length that ensures or increases volumetric injection of holes into the active region. 43. The method or device of any of the examples 1-42, wherein the active region and the PHW are coupled to, grown on, or grown as part of, the VLI. 44. The method of device of any of the examples 1-43, wherein examples of the V-defects include, but are not limited, to the (e.g., polyhedron) shaped structure 700 of Figure 7 or as shown and described in the reference by Yufeng Li et. al., entitled “Nanoscale Characterization of V-Defect in InGaN/GaN QWs LEDs Using Near-Field Scanning Optical Microscopy,” Nanomaterials 2019, 9, 633, http://dx.doi.org/10.3390/nano9040633, which reference is incorporated by reference herein. Advantages and Improvements of Section I embodiments V-shaped defects (commonly referred to as V-defects) have recently markedly improved the efficiency of LEDs, particularly in the yellow and green wavelengths, by diminishing their forward voltage and hence improving their wall-plug efficiency. However, the efficiency droop is not reduced compared to standard LEDs. This is due to the fact that, while all quantum wells (QWs) of the active layer are laterally injected thanks to the V-defects, they are only active on a short length determined by the hole diffusion length in the QWs from their injection point. An engineered structure is thus necessary to optimize the lateral hole injection to ensure or increase volumetric injection throughout the QWs, thereby reducing the efficiency droop. The hole diffusion length in the QWs cannot be readily improved as it is determined by electron-hole recombination. However, we can increase the hole diffusion length in the quantum barriers (QBs) separating the QWs as this hole diffusion length is not seriously limited by recombination because the local electron density is low due to the barrier height. Thus, the hole diffusion length in the QB is determined by the downfall of holes into the adjacent QWs. Here, we propose an engineered planar hole waveguide (PHW) design to enhance the laterally injected minority hole diffusion length in the QBs by introducing (i) thin AlGaN interlayers or (ii) thin Si-delta doped GaN layers near or just below each of the QWs. Advantages of embodiments of the present invention include: 1. Improve the efficiency of LEDs at high applied current density for high-power LEDs: Lower efficiency droop LEDs can be obtained. 2. Ease of implementation with industrially viable MOCVD growth. The method can be easily applied in the production line of any lighting companies. 3. This method can be applied to all wavelength LEDs and lasers. 4. Due to the deep hole injections, even white LEDs can be developed using this method. The white LED would be more efficient than conventional phosphor converted blue LEDs for solid-state lighting. 5. The white LEDs developed using this technique would provide higher modulation bandwidths compared to the conventional phosphor converted blue LEDs for visible-light communication. References for section I The following references are incorporated by reference herein. 1 J. Cho, E.F. Schubert, and J.K. Kim, Laser Photonics Rev.7, 408 (2013). 2 J. Iveland, L. Martinelli, J. Peretti, J.S. Speck, and C. Weisbuch, Phys. Rev. Lett.110, 177406 (2013). 3 F. Jiang, J. Zhang, L. Xu, J. Ding, G. Wang, X. Wu, X. Wang, C. Mo, Z. Quan, X. Guo, C. Zheng, S. Pan, and J. Liu, Photonics Res.7, 144 (2019).
Figure imgf000034_0001
5 A.E. Romanov, T.J. Baker, S. Nakamura, and J.S. Speck, J. Appl. Phys.100, 023522 (2006). 6 C.-K. Li, C.-K. Wu, C.-C. Hsu, L.-S. Lu, H. Li, T.-C. Lu, and Y.-R. Wu, AIP Adv.6, 055208 (2016). 7. Yufeng Li et. al., entitled “Nanoscale Characterization of V-Defect in InGaN/GaN QWs LEDs Using Near-Field Scanning Optical Microscopy, Nanomaterials 2019, 9, 633, http://dx.doi.org/10.3390/nano9040633 II. Engineered three dimensional carrier injectors for indium aluminum gallium nitride devices As described herein, hole injection is vertically inhomogeneous throughout the stack of QWs and only the top QWs, near the p-side of the LED heterostructure are populated by holes4,5 (in the remainder of this description, we call bottom QWs, the QWs that are grown nearest to the n-GaN layer, as the growth sequence of a basic LED structure is n-GaN followed by QWs followed by p-GaN) due to their larger effective mass compared to electrons. In longer wavelength LEDs, the larger internal polarization fields put a larger energy barrier to the hole transport. The limitation of hole transport leads to a very asymmetric current injection, with high carrier density in the top QWs. The high carrier density in the top QWs significantly increases droop as the top QWs bear the major part of injected carriers, thus leading to a larger local carrier density there compared to the expected situation where carriers would be equally distributed over all QWs. Hence, methods of carrier injection in the whole active volume, called hereafter volumetric carrier injection, are of substantial interest, as they would lead to low-droop GaN-based LEDs emitting at any wavelengths. V-shaped defects (commonly referred to as V-defects) have recently markedly improved the wall-plug efficiency of LEDs, particularly in the yellow and green wavelengths6 by reducing their forward voltage. Schematics of a V-defect in a multi- QW LED structure is shown in Figure 7. The improvement is attributed to the lateral hole injection obtained at the oblique (relative to the overall growth direction) plane of the V-defect. The lateral injection in the V-defect is local due to the smaller energy discontinuities between the QWs and the quantum barriers (QBs) for carriers travelling form the oblique p-type doped region, as schematically shown in Figure 8. Thus, the laterally injected holes would be immediately captured by the QWs at the edge of the lateral junction and recombine in all the QWs of the stack (Figure 8). However, the injected holes only survive for a small length in the QWs, the so-called diffusion length, and therefore the QWs are not injected homogeneously, laterally this time. Therefore, the lateral hole injection in a V-shaped defect does not significantly reduce local carrier densities and thus does not strongly affect the efficiency droop6. An engineered structure would then be necessary to optimize the lateral hole injection to ensure or increase or enables or allows volumetric injection to reduce the efficiency droop in all wavelengths. This section of the present disclosure describes a plurality of designs and geometries such as rectangular, pyramidal and triangular-ridge injectors to engineer the hole injection homogeneity and the efficiency droop in LEDs with different emission colors (Figure 9 and following). We shall call such structures three dimensionally (3D) engineered structures to differentiate them from the usual LED structures which rely on planar geometries. In 3D engineered structures, the geometries of active layers and contacts do not lie in the same or parallel planes as in planar structures. The proposed designs involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation (Figure 9). The active region structure designs are shown in Figure 9. In one or more examples, the structures are formed using a top-down approach in which a combination of dry, either inductively coupled plasma (ICP) or reactive ion etching (RIE), and wet etching (using KOH-based solutions such as AZ400K, AZ300MIF, TMAH, etc.) are used. Also, a photoresist reflow method is applied to obtain angled facet etch patterns with different inclination angles. In various examples, the inclination angles are controlled by the photoresist geometry which is controlled by the heating and consequently reflow condition. A conformal p-GaN layer (using epitaxy or solid-state diffusion method described below) at the sidewalls of the formed structures would ensure or allow or increase lateral hole injection in addition to the vertical injection. Therefore, a volumetric hole injection is obtained, which improves the efficiency droop as it could reduce carrier density for a given J. Such designs leading to sidewall injection scheme, hereafter called 3D injectors, can be formed by a combination of dry and wet etching process. A photoresist reflow7 method can be used to form different pattern shapes. The photoresist reflow method is a method to generate 3D structures by applying heat to the photoresist. First, a conventional photoresist pattern is generated on a sample. Then, by applying heat to the sample, the photoresist pattern is thermally treated above melting temperature of the photoresist. A convex shape is formed due to a strong surface tension of the liquid resist and the surface property of the sample. The convex geometry allows for dry etching with different facet sidewall inclination angles depending on the resist shape. The method can be used to generate different patterns with different sidewall inclination angles. Figure 10 shows cross-sectional scanning electron microscopy (SEM) images of several GaN trenches with only dry etching (Figure 10(a)) and dry etching plus wet etching using TMAH (Figure 10(b)). The engineering parameters for photoresist reflow is the thickness, heating temperature and duration of the heating. For dry etching, either using ICP or RIE, the etching conditions, including gas flows, RF etching power, etch rates and DC bias are engineering parameters. For wet etching, either using TMAH, AZ400K, AZ300MIF, phosphoric acid, and any other KOH-based solutions can be used. The engineering parameters for wet etching include wet etch time, solution concentration and temperature. Photo-induced chemical etching (also called photoelectrochemical or PEC etching) using KOH-based solutions with and without applied electrical bias can also be used as wet etching method. The initial conformal formation of p-GaN on the top and sidewalls of the mesa structures can be obtained using a novel Mg solid-state diffusion process described in Figure 11. A Mg layer followed by a Pd or Pt layer is deposited on an unintentionally doped (UID) or lightly doped GaN on sapphire, Si, SiC or freestanding GaN substrates. Upon elevating temperature (800 ^C to 1000 ^C), the Mg atoms start to diffuse to the UID or lightly doped GaN while Ga atoms migrate out of the surface toward the metallic layer and start to form a Gallide layer at the semiconductor-metal interface. Mg atoms replace Ga in the crystal and serve as acceptors. Without the need for another crystal epitaxy step, a layer of p-type GaN can therefore be obtained after removing the metal and the formed Gallide layers. The structures could remain 3D for fabrication or can be coalesced during a p-GaN overgrowth layer by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (Figure 12). A p-GaN layer can also be grown using NH3 pulsed-mode MOCVD growth methods, similar to growth of core-shell nanostructures8,9. The structures can then be processed using any standard LED processing procedure. The engineering parameters for the Mg diffusion method include annealing temperature (and consequently the Mg diffusion depth) and the thicknesses of the Mg layer and the metal layers. The Mg diffusion depth can also be as large as a whole triangular or rectangular mesa or trench. Also, the p-n junction formation by the Mg diffusion method should be less sensitive to the impurities from ambient exposure and the damage from dry etching at the top surface and sidewalls, since the p-n junction will form far from the top and sidewall surfaces. Hence, the method can also be used in micro-LEDs for micro-pixel displays and visible light communication, since the size-dependent LED efficiency drop is diminished by the described method here due to the reduced surface effects. An n+ layer can be considered below the UID or lightly doped GaN layer. Depending on the conditions (i.e. Mg diffusion condition and the thickness of the UID or lightly doped GaN above the n+ layer), either p-i-n or p-n junctions can be formed after the Mg diffusion. In addition, care should be considered to prevent or reduce direct hole injection in the n-layer (Figure 13(a)), which would be competing to injection into the QWs. To avoid this, the length of the Mg-diffused p-type sidewall can be engineered (Figure 13(b)). This may reduce the hole injection a bit in the very first QW (the nearest QW to the n-GaN). However, the impact of slight reduction in hole injection in one QW on the overall efficiency can be insignificant, as the total number of QWs can be very large in this method. Alternatively, the first layer could be a layer, either an alloy barrier layer such as a UID or n-type doped AlGaN, InAlN, or InAlGaN or an n-type delta doped layer such as Si or Ge delta-doped layer of sufficient thickness to play the role of a blocking barrier to the hole transport to the n-side of the junction (Figure 13(c)). The length of the p-GaN sidewalls, the thickness and composition of the alloy barrier layer or thickness and doping level of the n-type delta doped layer could be engineered to minimize hole injection into the n-GaN, while maintaining high efficiency. Similar method can be applied to other geometries shown in Figure 9. To avoid the direct diffusion of the Mg atoms to the MQW active regions and to avoid a potential generation of Shockley-Read-Hall (SRH) non-radiative recombination in the active region, the p-GaN can be formed by Mg diffusion into a UID GaN spacer which can be overgrown on the mesa active region by MOCVD or MBE. Figure 14 shows a cross-sectional schematic of this approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process. The steps include active region growth (Figure 14(a)), mesa etching (Figure 14(b)), dielectric mask for regrowth (Figure 14(c)), regrowth of 3D UID spacer layer (Figure 14(d)), conformal deposition of Mg layer and metal (Pt or Pd) layer on top of the spacer layer (Figure 14(e)), and formation of the 3D p-GaN over the active region by Mg diffusion to the regrown UID GaN spacer layer followed by the removal of the metal and Gallide layers (Figure 8(f)). Note that the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction (similar to other approaches discussed in Figure 13). Figure 15 schematically shows the fully processed LEDs in two particular 3D geometries. The LEDs of Figure 15 operate as follows: in spite of the shorter path between the n++-GaN and p-GaN layers through the UID GaN or lightly doped layer, electrons will preferentially travel through the InGaN QWs towards the p-contact. This is due to the higher built-in energy barrier of the n-GaN-p GaN junction compared to the energy barrier of the MQW heterostructure. This is clear from the turn-on voltage difference between GaN p-n junctions (about 3.2V) vs. that of MQW LEDs, typically below 2.8 V, dependent on the Indium composition in the QWs. Engineering parameters include size and distribution or the mesas, convex or concave geometries (whether mesa geometry or trench geometries), number of QWs, and thicknesses of the QWs/QBs. In addition to the top-down structures mesa structures (described above), the method described herein can similarly be applied to bottom-up nanostructures as well, for either planar (Figure 16(a)) or core-shell (Figure 10(b)) QW/QB designs. Both planar and core-shell active region geometries in the structures shown in Figure 16 can be controlled by growth conditions and thus growth kinetics and/or thermodynamics in MOCVD or MBE techniques. In the core-shell nanostructure- based light emitting devices the active regions can be grown on nanostructures using MOCVD or MBE on patterned substrates9. The p-GaN growth is normally non- uniform in such nanostructures leading to different thicknesses of p-GaN on the top and on the sidewall of the nanostructures8,9. The Mg solid-state diffusion (described in Figure 5) can be applied to the core-shell active region grown on the nanostructures resulting in uniform p-GaN formation across the nanostructures (Figure 10(b)). The uniform p-GaN facilitates the volumetric hole injection in the nanostructure-based light-emitting devices. To avoid the direct diffusion of the Mg atoms to the MQW active regions and to avoid a potential generation of SRH non-radiative recombination in the active region, the p-GaN can be formed by Mg diffusion into a UID GaN spacer which can be overgrown on the nanostructure active region by MOCVD or MBE. Figure 17 shows a cross-sectional schematic of this approach to avoid direct Mg diffusion into the active QWs during the Mg diffusion process. The steps include core-shell active region growth (Figure 17(a)), core-shell regrowth of a UID layer (Figure 17(b)), conformal deposition of Mg layer and metal layer (Figure 17(c)), and formation of a core-shell 3D p-GaN over the active region by Mg diffusion method followed by removal of the metal and Gallide layers (Figure 17(d)). Note that the dielectric mask can also be useful in avoiding direct hole injection from sidewall p-GaN to the n-side of the junction. (similar to other approaches discussed in Figure 13). Also, a similar approach can be applied to the nanostructure geometries shown in Figure 16 (a) to avoid direct Mg diffusion into the active QWs during the Mg diffusion process (similar to the method described in Figure 14). The presented invention can also be used to form 3D p-n junctions and to make fully lateral p-n junctions for power electronic applications. Figure 18 demonstrates an approach to make 3D lateral p-n junctions with the methods described in this invention. The widths of the p-GaN and n-GaN are arbitrary in this method, which provides a platform for p-n junctions with extreme dimensions which are not normally possible by vertical designs. For example, extremely wide drift regions are possible in this design which can provide very large reverse blocking voltages for power electronic applications. The depths of the isolation mesa etch and the dimensions of the Mg diffused p-GaN column could be other engineering parameters. Finally, both hetero- and homo-junction GaN-based nano lasers for photonics and nanometrology applications can be implemented using this method. III-nitride nanowire LEDs and lasers are potential building blocks for future photonic integrated circuits (PICs) and nanophotonic devices as light sources due to their tunable band gap and excellent waveguide properties. The proposed nanowire-based electrically injected lasers can be used in PICs and also in nanometrology10 as cantilever for atomic force microscopy and near-field scanning electron microscopy. Solar cell or photodetector designs including the 3D engineered structures can also be considered. Example Embodiments 1. Forming III-nitride light-emitting diodes comprising of intentional 3D engineered structures with vertical and lateral junctions. 2. The method of example 1, wherein the junctions are formed using Mg solid-state diffusion. 3. The method of example 1, wherein substrates with polar c-plane, either Ga-face or N-face, and/or nonpolar and/or semipolar orientations are used. 4. The method of example 1, wherein rectangular and pyramidal geometries are used. 5. The method of example 1, wherein different patterns including circles and stripes with different opening and pitch sizes and stripe orientations can be used. 6. Growth of LED structures with metalorganic chemical vapor deposition. 7. Top-down 3D engineered structure formation using combination of dry etching and wet etching. 8. The method of example 5, wherein a photoresist reflow method is used as mask layer to engineer the sidewall etch angle in the dry etching. 9. The method of example 5, wherein KOH-based solutions are used to remove the top and sidewall damage during dry etching. 10. The method of example 5, wherein TMAH, AZ400K, AZ300MIF, and phosphoric acid with different concentrations are used as wet etch solutions. 11. The method of example 1, wherein an unintentionally doped or lightly doped GaN layer is regrown prior to the Mg diffusion. 12. The method of example 1, wherein an underlying blocking barrier (an alloy barrier layer such as AlGaN, InAlN, or InAlGaN) is grown below the first QW (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct hole injection to the n-side of the junction. 13. The method of example 1, wherein an underlying blocking barrier (an n-type delta doped layer such as Si or Ge delta-doped layer) is grown below the first QW (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct hole injection to the n-side of the junction. 14. The method of example 1, wherein the length of the Mg-diffused p- GaN sidewalls is engineered to avoid direct hole injection into the n-side of the junction. 15. The Mg diffusion could be used in different temperatures to obtain different diffusion depths. 16. Due to the formation of p-type material at the sidewalls, volumetric hole injection is obtained for all the wells. 17. Reduction of the size-dependent efficiency drop of micro-LEDs using the described method for micro-pixel display and visible-light communication. 18. Engineered large number of QWs for very high active region volume to enhance efficiency and reduce droop. 19. The method can be applied to all visible wavelengths by changing the active region alloy composition. 20. Method of white light generation using stacks of RGBY QWs in a single LED on a single chip by stacking QWs emitting at different wavelengths, laterally injected. 21. The described method applied to both top-down and bottom-up light emitting structures. 22. The described method applied to bottom-up core-shell and non-core- shell geometry light emitting structures. 23. The described method applied to nanostructure-based light-emitting structures. 24. The described method applied to other III-V material systems. 25. The described method applied to GaN-based top-down and bottom-up nanostructure lasers for photonics and nanometrology applications. 26. The described method applied to GaN-based 3D p-n junctions for power electronic applications. 27. The described method applied to other structures such as UV LEDs and lasers. 26. A solar cell or detector including the 3D engineered structures as described herein. Further examples 1. Figures 15-17 illustrate a device 1500, comprising: an array of three dimensionally (3D) engineered structures 1502 (e.g., a mesa) each comprising an active region 1504 comprising III-V material and a plurality of quantum wells 1506; and a vertical junction 1508 and a lateral junction 1510 with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction. 2. The device of example 1, further comprising a p-type layer 1512 on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region. 3. The device of example 1 or 2, further comprising: an n-type III-V layer 1514 providing electrons to the quantum wells; a p-type layer 1512 on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the quantum wells on the sidewall so as to inject holes laterally into each of the quantum wells; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer 1516 between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer and the 3D engineered structures. 4. The device of example 3, wherein the p-type layer 1512 comprises p- type dopants diffused from a dopant layer deposited on the p-type layer. 5. The device of example 4, wherein the III-V layer 1516 comprises GaN, the p-type layer comprises p-type GaN, the dopant layer comprises a Magnesium layer, and the p-type dopants comprise Magnesium. 6. The device of examples 1-5, further comprising a hole blocking barrier layer 1518 between the n-type layer 1514 and the active region 1504 so as to prevent or reduce direct hole injection to the n-side of the junction 1520 with the active region. 7. The device of example 6, wherein the hole blocking layer comprises AlGaN, InAlN, or InAlGaN. 8. The device of example 6, wherein the hole blocking layer comprises an n-type delta doped III-V layer (e.g., but not limited to as Si-delta doped GaN or Ge- delta doped GaN). 9. The device of examples 1-8, wherein the device 1500 comprises a laser or light emitting diode and the III-V material and III-V layer comprise III-nitride. 10. The device of examples 1-9, wherein the sidewalls 1522: are inclined at an angle 1524 of less than 45 degrees, or at an angle between 45 degrees and 60 degrees, with respect to a base 1530 of the 3D engineered structures so as to increase surface area contact of the quantum wells with the p-type layer 1512. 11. The device of examples 1-9, wherein the 3D engineered structures 1502 have the sidewalls 1522 forming a convex or concave geometry. 12. The device of examples 1-11, wherein the sidewalls 1522 have a truncated triangular shape, or the 3D engineered structures 1502 comprise a pyramidal shape. 13. Figure 15(c) illustrates a method of making a device, comprising: forming a device 1500 comprising three dimensionally (3D) engineered structures each comprising an active region (as illustrated in Block 1580); and forming a vertical junction and a lateral junction with each of the 3D engineered structures, wherein holes are injected into the active region through the vertical junction and the lateral junction (as illustrated in Block 1582). 14. The method or device of example 13, wherein the junctions are formed using Mg solid-state diffusion. 15. The method or device of any of the preceding examples, further comprising growing the light emitting device on a substrate having polar c-plane, either Ga-face or N-face, and/or nonpolar and/or semipolar orientation. 16. The method or device of any of the preceding examples, wherein the 3D engineered structures have a rectangular, triangular, circular, or a pyramidal geometry. 17. Figure 15(c) illustrates the method or device of any of the preceding examples, further comprising: patterning the 3D engineered structures with different patterns, including selecting a pitch and orientation of openings and stripes around the 3D engineered structures (the forming step of Block 1580 may include patterning the 3D engineered structures). 18. Figure 15(c) illustrates the method or device of any of the preceding examples, further comprising growing the light emitting device using metalorganic chemical vapor deposition (the forming step 1580 may include growing device layers). 19. The method or device of any of the preceding examples, comprising forming 3D engineered structure from a top down using a combination of dry etching and wet etching. 20. Figure 15(c) illustrates the method or device of example 19, wherein the forming of Block 1580 comprises patterning the 3D engineered structures using photoresist, including depositing photoresist as a mask layer and reflowing the photoresist to engineer a sidewall etch angle of the 3D engineered structures during the dry etching. 21. The method or device of examples 19 or 20, wherein potassium hydroxide (KOH)-based solutions are used to remove the damage to the top and sidewalls of the 3D engineered structures during the dry etching. 22. The method or device of examples 19-21, wherein TMAH, AZ400K, AZ300MIF, and phosphoric acid with different concentrations are used as wet etch solutions during the wet etching. 22. The method or device of any of the preceding examples, further comprising re-growing an unintentionally doped or lightly doped GaN layer on the 3D engineered structures prior to performing Mg diffusion in the GaN layer. 23. Figure 9, 11, 12, 15B illustrate the method or device of any of the preceding examples, wherein forming the device (Block 1580) further comprises: growing an n-GaN layer 1514 or n-type III-nitride layer; growing the active region 1504 comprising multi quantum wells (MQW); and growing an underlying blocking barrier layer 1518 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region, and forming (e.g., patterning) the 3D engineered structures 1502 to include the active region. 24. The method of example 23, wherein the blocking layer comprises a barrier layer including AlGaN, InAlGaN, or InAlGaN. 25. The method of example 23, wherein the blocking layer comprises an n- type delta doped layer (comprising, but not limited to, a Si delta doped layer or a Ge delta doped layer). 26. Figure 12 illustrates the method or device of any of the preceding examples, further comprising engineering or selecting a length of the Mg-diffused p- GaN sidewalls or Mg-diffused III-nitride sidewalls 1522 to avoid direct injection of holes into an n-side of the junction with the active region, as illustrated in forming of junctions step of Block 1582. 27. The method or device of examples 14, 22, or 26, further comprising selecting a temperature and time of the Mg diffusion to obtain a desired diffusion depth of the Mg. 28. Figure 12 illustrates the method or device of any of the preceding examples, further comprising forming p-type material 1512 at the sidewalls 1522 of the 3D engineered structures so as to achieve volumetric injection is obtained for all the wells (can be performed in the forming of junctions step 1582). 29. The method or device of any of the preceding examples, wherein: the light emitting device comprises a micro LED, and the 3D engineered structures reduce the size-dependent efficiency drop of the micro-LEDs in a micro-pixel display or visible light communication system. 30. The method or device of any of the preceding examples, further comprising increasing a number of quantum wells in the active region 1504 so as to increase a volume of the active region, thereby enhancing or tailoring efficiency of the light emitting device and reducing current droop of the light emitting device. 31. The method or device of any of the preceding examples, further comprising selecting an alloy composition of the active region 1504 so as to obtain the light emitting device emitting electromagnetic radiation having any visible wavelength. 32. Figures 15B, 9, and 11-12 illustrates the method or device of any of the preceding examples, further comprising: growing the active region 1504 of the light emitting device comprising a stack of quantum wells, each of the quantum wells configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength (can be grown in the forming step of Block 1580); and wherein the stack is laterally injected with holes. 33. The method or device of any of the preceding examples, wherein the light emitting device comprises a III-nitride LED or III-nitride laser. 34. The method or device of any of the preceding examples, wherein the light emitting device emits ultraviolet light. 35. The method or device of any of the preceding examples, wherein the light emitting device comprises a top-down or bottom-up light emitting structure. 36. The method or device of any of the preceding examples, wherein the light emitting device comprises a bottom-up core-shell or a non-core-shell geometry light emitting structure. 37. The method or device of any of the preceding examples, wherein the light emitting device comprises a nanostructure-based light-emitting structures. 38. The method or device of any of the preceding examples, wherein the light emitting device comprises a III-V material system. 39. The method or device of any of the preceding example, wherein the light emitting device comprises a GaN-based top-down or bottom-up nanostructure lasers for photonics and nanometrology applications. 40. Figures 15B, 9, 11-12 illustrates the method or device of any of the preceding examples, further comprising forming a p-type layer on a sidewall and a top of each of the 3D engineered structures, including (can be formed in the junction forming step of i Block 1582): growing a III-nitride layer 1100 on the top and sidewall of each of the 3D structures (Figure 11a); depositing an Mg layer 1102 on the III-nitride layer (Figure 11b); depositing a metal layer 1104 on the Mg layer, the metal layer including Pt or Pd (Figure 11c); and heating the structure to a temperature above 800 degrees Celsius so as to cause diffusion of the Mg from the Mg layer into the III-nitride layer 1100, thereby forming a p-type doped layer 1106, 1512 in the III-nitride layer 1100 (Figure 11f). 41. The method or device of any of the preceding examples, wherein the 3D engineered structures each comprise mesas, the quantum wells are separated by quantum barriers, and the quantum wells and the quantum barriers comprise III- nitride material. 42. Figures 15A-15B further illustrate the method or device of any of the preceding examples, comprising a hole blocking layer between the n-type layer and the active region, the hole blocking layer: comprising an alloy barrier layer 1518 (e.g., but not limited to, unintentionally doped or n-type doped AlGaN, InAlN, or InAlGaN) and/or or an n-type delta doped layer (e.g, but not limited to a Si or Ge delta-doped layer), and the hole blocking layer of sufficient thickness to block hole transport of holes to the n-side of the junction. The hole blocking layer can be formed/deposited during the forming of the device structure step of Block 1580). 43. Figures 12 and 15A-15B further illustrate the method or device of any of the preceding examples, comprising: the p-type layer 1512 formed on or above a top and sidewall 1522 of each of the 3D engineered structures 1502, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region, and the p-type layer 1512 formed by magnesium diffusion into an unintentionally doped III-nitride layer overgrown on the active region, the p-type layer avoiding (1) direct diffusion of Mg atoms to the quantum wells in the active region and/or (2) generation of Shockley-Read-Hall (SRH) non-radiative recombination in the active region. 44. Figures 9-15A-15B further illustrate the method or device of example 43, wherein: fabrication of the device includes (block 1580): growing the active region, etching a mesa including the active region, depositing a dielectric mask (Block 1582 during forming of junction step 1582)); using the mask to selectively grow the III-nitride layer 1100 (e.g., GaN) on the top and the sidewalls of the mesa (during step 1582), Figure 11a conformally depositing an Mg layer 1102 and a metal 1104 (e.g., but not limited to Pt or Pd) layer on top of the III-nitride layer (Figure 11b, step 1582), and formation of the p-type layer 1512 over the active region by Mg diffusion to the III-nitride layer (Figure 11c, step 1582); and removing the metal layer and a Gallide layer formed during the Mg diffusion (Figure 11f, step 1582). 45. The device of any of the preceding examples, wherein the device comprises a hetero- and homo-junction GaN-based nano laser or LED for photonics and/or nanometrology applications 46. The device of example 45, wherein the nanolaser or nano LED comprises a III-nitride nanowire LED or a nanowire laser useful as a building block in a photonic integrated circuits (PIC) or as a light source. 47. The device of any of the preceding examples, wherein the device is a light emitting device, a solar cell, a detector, or a transistor. 48. The device of example 47, wherein: the light emitting device 1500 emits light in response to electrons recombining with holes in the active region 1504, the electrons provided from the n-type layer and the holes provided from the p-type layer, or the active region in the device comprising the solar cell generates holes and electrons in response to electromagnetic radiation absorbed in the active region. 49. The device of any of the preceding examples, wherein the device comprises a planar or a core shell structure, the core shell comprising the p-type layer forming a shell on a core comprising the active region, the device formed using a top- down or bottom-up geometry. 50. The device of one or more of the preceding examples, wherein the device comprises a transistor useful in a power electronics application. 51. Figure 18 illustrates a device 1800 useful in a power electronics application (e.g., transistor), comprising: an array of three dimensionally (3D) engineered structures 1802 (e.g., a mesa) each comprising III-V material and a p-n junction 1804 between a p-type layer/region 1806 and an n-type layer/region 1808; the p-n junction comprising a vertical junction 1810 and a lateral junction 1812, wherein holes are injected through the vertical junction and the lateral junction. 52. A method for fabricating the device of example 51, wherein widths W of the p-type layer 1806 and the n-type layer 1808 are arbitrarily tuned to obtain dimensions not possible in a device having only a vertical junction. 52. Figure 18 further illustrates a method for fabricating the device of example 51, comprising fabricating a transistor including the p-n junction and having a drift region sufficiently wide to provide very large reverse blocking voltage desirable for power electronic applications, the method further comprising tailoring an isolation mesa etch used to fabricate the 3D engineered structures and the dimensions of a Mg diffused p-GaN layer formed on the p-type layer. Advantages and Improvements of the methods and devices of section II. The advantages of the LED structure designs described herein include (i) low- droop InGaN-based RGBY LEDs by volumetric hole injection, (ii) more design freedom for thick active regions with large number of QWs for high efficiency, (iii) improved efficiency of green LEDs and contribute to solve the green gap, and (iv) mitigation of the size-dependent efficiency drop in micro-LEDs due to the reduced surface effects. In certain geometries, the designs described herein may also partially increase lateral optical confinement in the active region. For instance, the triangular/pyramidal geometry has the advantage of redirecting photons towards the extraction cone of the substrate/air interface, the more so with angle optimization. It also has the advantage of injecting more electrons in the lower QWs up, thus reducing the excess voltage. The position of the junctions within the MQWs (determined by the Mg diffusion length) can be adjusted by the duration and temperature of the Gallide process, to optimize uniformity of carrier injection. A thicker p-GaN can also be grown by MOCVD/MBE on top of the p-GaN obtained by Mg diffusion method to planarize the structure for ease of processing (Figure 6). An engineered large number of QWs for all wavelengths can be used in the active region without the issues with hole injections in the deeper wells. In particular, white LEDs on a single wafer can be obtained by designing active RGBY QWs with different emission colors on a single structure on a single chip. The white LED processed using this method has the advantage of higher efficiency and higher modulation bandwidth compared to any conventional phosphor-converted white LEDs (with inefficient and slow phosphor conversion process) and can be used in solid-state lighting as well as visible-light communications. The method can be applied to light emitting structures with different crystal orientations. This method can be similarly applied to other III-nitride light emitting structures such as UV LEDs, and lasers. An application of the method in electrically injected nanostructures can be used in PICs and nanometrology. Also, the method can be used in 3D p-n diodes for fully lateral p-n junctions for power electronics. Solar cell or photodetector designs including the 3D engineered structures can also be considered based on this invention. Commercial advantages of the method include: 1. Improvement of the efficiency of LEDs at high applied current density for high-power LEDs: Lower efficiency droop LEDs can be obtained. 2. Implementation with industrially viable MOCVD growth. The method can be applied in the production line of any lighting company. 3. This method can be applied to all wavelength LEDs and lasers. 4. Due to the deep hole injections, even white LEDs can be developed using this method. The white LED would be more efficient (with also higher color- rendering index) than conventional phosphor convert d blue LEDs for solid-state lighting. 5. The white LEDs developed by this method can provide higher modulation bandwidth compared to the conventional phosphor converted blue LEDs for visible-light communication. 6. Due to the very high volume injection and improved efficiency, ultraviolet to infrared LEDs for high-power applications can be obtained. 7. Several other areas, including photonic integrated circuits, nanometrology, and power electronics can be affected by this invention. References for second section The following references are incorporated by reference herein. 1 D. Feezell and S. Nakamura, Comptes Rendus Phys.19, 113 (2018). 2 J. Cho, E.F. Schubert, and J.K. Kim, Laser Photonics Rev.7, 408 (2013). 3 J. Iveland, L. Martinelli, J. Peretti, J.S. Speck, and C. Weisbuch, Phys. Rev. Lett.110, 177406 (2013). 4 A. David, M.J. Grundmann, J.F. Kaeding, N.F. Gardner, T.G. Mihopoulos, and M.R. Krames, Appl. Phys. Lett.92, 053502 (2008). 5 C.-K. Li, M. Piccardo, L.-S. Lu, S. Mayboroda, L. Martinelli, J. Peretti, J.S. Speck, C. Weisbuch, M. Filoche, and Y.-R. Wu, Phys. Rev. B 95, 144206 (2017). 6 F. Jiang, J. Zhang, L. Xu, J. Ding, G. Wang, X. Wu, X. Wang, C. Mo, Z. Quan, X. Guo, C. Zheng, S. Pan, and J. Liu, Photonics Res.7, 144 (2019). 7 D. Li, editor , in Encycl. Microfluid. Nanofluidics (Springer US, Boston, MA, 2008), pp.1642–1643. 8 M. Nami, A. Rashidi, M. Monavarian, S. Mishkat-Ul-Masabih, Ashwin.K. Rishinaramangalam, S.R.J. Brueck, and D. Feezell, ACS Photonics 6, 1618 (2019). 9 M. Nami, I.E. Stricklin, K.M. DaVico, S. Mishkat-Ul-Masabih, A.K. Rishinaramangalam, S.R.J. Brueck, I. Brener, and D.F. Feezell, Sci. Rep. 8, 501 (2018). 10 M. Behzadirad, M. Nami, A.K. Rishinaramagalam, D.F. Feezell, and T. Busani, Nanotechnology 28, 20LT01 (2017). III. Hole injection by p-type active regions and lateral injectors in InAlGaN light-emitting devices and methods thereof This section of the present disclosure describes novel LED designs, wherein the MQW active region is fully or partially p-type doped. Locating the active QWs in the p-side of the junction eliminates the issue with hole injection in conventional LEDs, where the active QWs are located in the unintentionally doped (UID) region of the junction (between p- and n-regions). Figure 19(a) and (b), respectively, show the structure of a full standard LED and an LED design according to the present invention. As opposed to the standard design (Figure 19 (a)), the design (Figure 19 (b)) according to the present invention comprises a top-down approach, including a combination of dry and wet etch to fabricate the structures, and conformal p-GaN formation using a Mg solid-state diffusion approach described below. To make the active region p-type, the QWs and/or QBs can be doped by Mg during the metal-organic chemical vapor deposition (MOCVD) growth prior to the mesa formation. Doping the QBs is more favorable to avoid Mg acting as non- radiative defect centers within the QWs. The profile of the p-type doping can be either uniform doping or modulation doping. With modulation doping, we can consider delta doping of Mg (a thin but high-concentration layer of dopant) in the QB regions. Engineering parameters for the modulation doping include the thickness, position with respect to the edges of the QBs, and doping levels. Limited Mg delta doping of a selected number of QBs have shown to have a positive impact on peak efficiency and efficiency droop in InGaN LEDs6. The lateral volumetric hole injection illustrated herein is essential and is necessary to ensure or increase or allow hole injection into all the stacked QWs (Figure 20). For standard LED designs without lateral hole injectors, the p-type doping of the active region (Figure 20(b)) does not significantly improve the hole injection in MQW designs compared to structures with UID active regions (Figure 20(a)). This is due to the large hole effective mass, very poor current spreading properties and high spreading resistance of the holes in the p-layer. As a result, holes are poorly injected from one QW to the next one, starting from the p-GaN top layer: The pre-existing holes due to doping would be rapidly exhausted by recombination with injected electrons. However, in a design according to the present invention, where a lateral hole injector is considered in addition to the p-type active region design, the holes can spread more evenly throughout the MQW active region (Figure 20(c)) from the sidewall of the MQW stack. Example Band Structures Figure 21 illustrates an idea of the present invention more closely and in further detail. In a band structure of a standard LED, where the QW active region is located in the UID region of the diode, the electron distribution is uniform while the hole distribution is very inhomogeneous (Figure 21(a)). This is due to the fact that hole effective mass is significantly larger than that of the electrons. The situation is even worse for longer wavelength InGaN LEDs where internal polarization creates an additional barrier to the hole transport. The limitation of hole transport leads to a very inhomogeneous current injection, the nearest QWs to the p-side of the junction receiving most of the current (Figure 21(a)), having large carrier densities, and hence large Auger non-radiative recombination, leading to significant droop – largely independent of the number of QWs. Hence, as shown in Figure 21(a), only the first few QWs near the p-side of the junction are populated by holes, which increases the effective carrier concentration for a given J, and thus increases the droop (because the droop is due to a cubic Auger non-radiative recombination process). To the contrary, Figure 21(b) shows a design according to the present invention where all the QWs are located in the p-side of the junction and all the QWs are populated by holes as they are the majority carriers in the p-side. As a result, all the QWs can contribute to the recombination process and thus improve the efficiency and efficiency droop. Note that the electron density would be high in all the QWs due to the ability of electrons to transport from one QW to another. Either a p-n diode or a p-i-n diode (containing a UID layer in between the n- and p-regions) can be used. The doping levels in both sides of the junction can be tailored to engineer the depletion width (Figure 21) for a given applied bias. A UID layer between the p- and the n-region can be included as shown in Figure 21(b) (indicated as UID depletion). The thickness of the UID layer can be engineered to obtain optimum electron transport to the p-side of the junction. Also, the UID layer below the active MQW region could contain a superlattice to improve material quality, carrier injection (lower effective energy gap than GaN) and forward voltage. In addition, the UID layer below the active MQW region could comprise a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection (progressively lower energy gap than GaN) and forward voltage. Example Doping Profiles Figure 22(a) and (22b) illustrate two example profiles of modulation doping that can be used make the active region p-type: (i) uniform doping (Figure 22(a)) and (ii) localized “d” doping (Figure 22(b)). Both of the doping profiles can be implemented during MOCVD growth of the active region. To avoid the potential non- radiative effect of Mg dopant, only QBs are doped in any of the two profiles. In the uniform doping of the QBs, the Mg dopants would randomly distribute across the QBs (Figure 22(a)), while the Mg atoms are concentrated in the d doping profile (Figure 22(b)). Example doping profiles include the QB average concentration of the Mg being similar in the two profiles, while the peak Mg concentration in the d modulation doping profile is between ~ 1018 cm-3 and ~ 1020 cm-3. Engineering parameters for the active region doping include the doping profile, thickness, position with respect to the edges of the QBs, and doping levels. In one or more examples, the designs described herein involve growth of MQW active regions followed by a triangular or rectangular mesa and/or stripe formation. The structures can be formed using a top-down approach in which a combination of dry etching (e.g., either inductively coupled plasma (ICP) or reactive ion etching (RIE)) and wet etching (e.g., using KOH-based solutions) may be used. In one or more examples, a photoresist reflow method can also be applied to obtain angled facet etch patterns with different inclination angles. The inclination angles can be controlled by the photoresist geometry which is controlled by the heating and consequently reflow condition. A conformal p-GaN layer (using epitaxy or a solid- state diffusion method described below) at the sidewalls of the formed structures would ensure or allow or increase lateral hole injection in addition to the vertical injection. As mentioned above, the lateral hole injectors can be formed by a combination of a dry and wet etching process. A photoresist reflow7 method can be used to form different pattern shapes. The photoresist reflow method is a method to generate 3D structures by applying heat to the photoresist. First, a conventional photoresist pattern is generated on a sample. Then, by applying heat to the sample, the photoresist pattern is thermally treated above melting temperature of the photoresist. A convex shape is formed due to a strong surface tension of the liquid resist and the surface property of the sample. The convex geometry allows for dry etching with different facet sidewall inclination angles depending on the resist shape. The method can be used to generate different patterns with different sidewall inclination angles. Figure 23 shows cross- sectional scanning electron microscopy (SEM) results of several GaN trenches with only dry etching (Figure 23(a)) and dry etching plus wet etching using Tetramethylammonium hydroxide (TMAH) (Figure 23(b)). The engineering parameters for photoresist reflow include the thickness, heating temperature and duration of the heating. Engineering parameters for dry etching (e.g., either using ICP or RIE) comprise the etching conditions, including gas flows, RF etching power, etch rates and DC bias. For wet etching, TMAH, AZ400K, AZ300MIF, phosphoric acid, or any other KOH-based solutions can be used. The engineering parameters for wet etching include wet etch time, solution concentration and temperature. Photo-induced chemical etching (also called photoelectrochemical etching or PEC) using KOH- based solutions (for example) with and without applied electrical bias can also be used as a wet etching method. Mg Solid State Diffusion The initial conformal formation of p-GaN on the top and sidewalls of the mesa structures can be obtained using a novel Mg solid-state diffusion process described in Figure 24. An Mg layer or an Mg compound layer such as MgF2 followed by a Pd or Pt layer is deposited on a UID or lightly doped GaN on sapphire, Si, SiC or freestanding GaN substrate. Upon elevating temperature (800 ^C to 1000 ^C), the Mg atoms start to diffuse to the UID or lightly doped GaN while Ga atoms migrate out of the surface toward the metallic layer and start to form a Gallide layer at the semiconductor-metal interface. Mg atoms replace Ga in the crystal and serve as acceptors. Without the need for another crystal epitaxy step, a layer of p-type GaN can therefore be obtained after removing the metal and the formed Gallide layers. A post activation annealing process may be required to remove the F atoms (which might have penetrated into the layers during the diffusion process) to ensure high electrical conductivity of the p-type material. A p-GaN layer can also be grown using NH3 pulsed MOCVD growth methods, similar to growth of core-shell nanostructures8,9. The structures will then be processed using standard LED processing. The engineering parameters for the Mg diffusion method include annealing temperature (and consequently the Mg diffusion depth), the thicknesses of the Mg layer and the metal layers. The Mg diffusion depth can also be as large as a whole triangular or rectangular mesa or trench. Also, the Mg diffusion method should be less sensitive to the impurities from ambient exposure and the damage from dry etching at the top surface and sidewalls, since the p-n junction will form far from the top and sidewall surfaces. Hence, the method can also be used in micro-LEDs as micro-pixel displays and visible light communication, since the size-dependent LED efficiency drop is diminished by the described method here due to the reduced surface effects. Depending on the conditions, either p-i-n or p-n junctions can be generated. Prevention or reduction of direct hole injection into the n-layer Also, care should be considered to prevent or reduce direct hole injection in the n-layer (Figure 25 and 26), which would be competing for injection into the QWs. One approach to avoid this is to deposit a conformal dielectric layer to passivate the sidewall prior to the Mg diffusion (Figure 25). Engineering parameters include thickness and dielectric material (SiNx, SiO2, etc.) and deposition method (plasma- enhanced chemical vapor deposition, atomic layer deposition, sputtering, etc.). In addition, the length of the Mg-diffused p-type sidewall and/or mesa etch depth can be engineered (Figures 26(a-d)). This may slightly reduce the hole injection in the very first QW (the nearest QW to the n-GaN). However, the impact of slight reduction of hole injection in one QW on the overall efficiency can be insignificant, as the total number of QWs can be very large in this method. Alternatively, the first layer could be an unintentionally doped or n-type doped AlN, AlGaN, InAlN, or InAlGaN layer or n-type delta doped layer of sufficient thickness to play the role of a blocking barrier to hole transport (Figures 26(e) and 26(f)). The length of the p-GaN sidewalls, the mesa etch depth, the thickness and composition of the underlying barrier layer, doping and thickness of n-type delta doped layer could be engineered to minimize hole injection into the n-GaN, while maintaining high efficiency. Similar methods can be applied to other geometries. Prevention or reduction of direct Mg diffusion into the active QWs To avoid direct Mg diffusion to the active QWs by Mg solid-state diffusion, we can also perform a UID GaN regrowth on the active mesa structures to cap the active region prior to Mg diffusion (Figure 27). The dielectric mask layer used for regrowth can be kept intact throughout the process as it would also avoid direct hole injection from the sidewall p-GaN to the n-side of the junction. The UID regrowth can be performed by a pulsed NH3 MOCVD method9. The growth conditions (such as temperature, pressure, V/III ratio and NH3 pulse duty cycle and on/off times) are the engineering parameters which control the shape and quality of the regrown UID layer. Other controlling parameters include the mesa etch depth, dielectric mask thickness, and p-GaN sidewall length. In addition to the top-down process described here, we can also consider bottom-up approaches using core-shell nanostructures. In either case, the p-GaN can be uniformly formed using Mg solid state diffusion described in Figure 24 and throughout this invention. The core-shell geometry has an additional advantage of ultra-large active region volume, which can further reduce the effective carrier density and efficiency droop. To avoid direct Mg diffusion into the active QWs during the Mg diffusion process in nanostructure geometries, a similar approach as described above can be applied, which would be similar to the method described in Figure 27. Example Device Structures Figure 28 shows a couple of processed LED designs using the methods described herein according to embodiments of the present invention. Arrays of the mesa structures can also be implemented to enhance the optical power, where the density and distribution of the structures are the engineering parameters. Various geometries such as pyramids, rectangular shapes, and cylindrical shapes can also be used for this design. The structures can be grown on various substrates, including planar and patterned Sapphire, Si, SiC, and freestanding GaN. The structures can also be grown on nonpolar, semipolar or polar orientations. Either the whole active region structure can be p-type doped or part of the active region can be unintentionally doped and part of it could be p-type doped. Depending on the wavelength range and current-voltage characteristics desired, the active region will comprise InGaN/GaN or InGaN/InGaN QWs/QBs for visible emitters emitting visible light, or AlGaN/AlGaN or GaN/AlGaN QWS/QBs for ultraviolet emitters emitting ultraviolet electromagnetic radiation. So far we have targeted top-down fabricated structures. However, as mentioned, this method can similarly be applied to grown bottom-up structures as well, for either planar or core-shell QW/QB designs. In the core-shell nanostructure- based light emitting devices, the active regions can be grown on nanostructures using MOCVD or MBE on patterned substrates9. The p-GaN growth is normally non- uniform in such nanostructures leading to different thicknesses of p-GaN on the top and on the sidewall of the nanostructures8,9. The Mg solid-state diffusion (described in Figure 6) can be applied to the core-shell active region grown on the nanostructures resulting in uniform p-GaN formation across the nanostructures. Further Device and method examples 1. Figure 19(b), 20(c) and 29 illustrate a method of making a device 1900, comprising: forming a light emitting device 1902, photodetector 1902, or solar cell 1902 comprising intentionally three dimensionally (3D) engineered structures 1904 with vertical and lateral junctions 1906 (vertical junction 1906a and lateral junction 1906b). Figure 29 illustrates an example wherein the method comprises forming the device structure including the 3D engineered structures (Block 2900) and forming the vertical and lateral junctions (Block 2902) with the 3D engineered structures. 2. The method of example 1, further comprising locating the active region 1908 of the device in a p-side of the junction by p-type doping. 3. The method of example 2, wherein the p-type doping of the active region is performed using metal-organic chemical vapor deposition. 4. The method of example 3, further comprising an unintentionally doped (UID) layer 1910 between the p- region 1912 and the n-region 1914. 5. The method of example 4, wherein: the active region 1908 comprises a multi quantum well (MQW) active region, the UID layer 1910 is below the MQW active region and contains a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN. 6. The method of example 4, wherein: the active region 1908 comprises a multi quantum well (MQW) active region, the UID layer 1910 below the MQW active region comprises a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN. 7. The method of example 3, wherein the p-type doping comprises performing a uniform or non-uniform p-type doping of the quantum wells (QWs) and quantum barriers (QBs) in the active region of the device. 8. The method of example 3, wherein the p-type doping comprises performing a uniform doping of Mg in the QBs of the active region. 9. The method of example 8, wherein the p-type doping comprises Mg delta doping of the QBs. 10. The method of example 9, wherein the delta Mg-doping occurs in the middle of each of the QBs. 11. The method of example 2, wherein the p-type doping of the active region is performed using Mg solid-state diffusion. 12. The method of example 1, wherein the junctions are formed using Mg solid-state diffusion. 13. The method of example 1, further comprising growing the device on a substrates 1950 having a polar c-plane (either Ga-face or N-face) orientation, a nonpolar orientation, or a semipolar orientations (e.g., FS or free standing Gallium Nitride). 14. The method of example 1, further comprising forming the 3D engineered structures with a rectangular or pyramidal geometry. 15. The method of example 1, further comprising patterning the 3D engineered structures with a patterns (e.g., the structures disposed in a pattern of circles or stripes), including selecting a pitch and orientation of openings and stripes around the 3D engineered structures. 16. The method of example 1, further comprising growing the devices with metalorganic chemical vapor deposition. 17. The method of example 1, comprising forming 3D engineered structure from a top-down approach using a combination of dry etching and wet etching. 18. The method of example 1, further comprising patterning the 3D engineered structures using photoresist, including depositing photoresist as a mask layer and reflowing the photoresist to engineer a sidewall etch angle of the 3D engineered structures during the dry etching. 19. The method of example 18, wherein KOH-based solutions are used to remove the damage to top and sidewalls 1916 of the 3D engineered structures caused during the dry etching. 20. The method of example 17, wherein TMAH, AZ400K, AZ300MIF, and phosphoric acid with different concentrations used as wet etch solutions during the wet etching. 21. Figure 19(b), 20(c), 24, and Figure 29 illustrates the method of any of the preceding examples, wherein forming the vertical/lateral junction 1906 in block 2902 further comprises forming a p-type layer 1918 on a sidewall 1916 and a top of each of the 3D engineered structures, including: growing a III-nitride layer 2400 on the top and sidewall of each of the 3D structures (Figure 24a); depositing an Mg layer or Mg compound layer 2402 such as MgF2 on the III- nitride layer (Figure 24b); depositing a metal layer 2406 on the Mg layer, the metal layer including Pt or Pd (Figure 24c); and heating the structure to a temperature above 800 degrees Celsius so as to cause diffusion of the Mg from the Mg layer into the III-nitride layer, thereby forming a p- type doped layer 2408, 1918 in the III-nitride layer (Figure 24d) and optional removal of the metal layer (Figure 24f). 22. The method of example 21, wherein forming the vertical/lateral junction in block 2902 further comprising a post activation annealing process to ensure high electrical conductivity of the p-type material. 23. The method of example 21, wherein the III-nitride layer 2400 comprises an unintentionally doped or lightly doped GaN layer regrown prior to the Mg diffusion. 24. The method of example 23, wherein the regrown layer 2400 is grown by MOCVD or MBE methods. 25. The method of example 23, wherein the regrown layer 2400 is grown by a pulsed NH3 MOCVD method. 26. Figure 29 illustrates the method of example 1, wherein forming the device structure in Block 2900 comprises forming the 3D engineered structures each comprising a mesa structure 1960, the method or step of Block 2900 further comprising depositing a conformal dielectric mask layer at the bottom corner of the mesa structures as a hole blocking layer 2600 to prevent or reduce direct hole injection to the n-side of the junction. 27. Figure 20(c), Figure 26, and Figure 29 illustrate the method of any of the preceding examples, wherein forming the device structure in block 2900 further comprises: growing an n-GaN layer 1917 or n-type III-nitride layer; growing the active region 1908 comprising multi quantum wells; and growing: an underlying alloy blocking barrier layer 2600 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region, and/or an n-type delta doped layer 2600 below the first quantum well (nearest to the n-GaN) as a hole blocking layer to prevent or reduce direct injection of holes to the n-side of the junction with the active region. In one or more examples, the forming step 2900 further comprises patterning, etching, or forming the 3D engineered structure (e.g., mesa) in the device structure. 28. The method of example 27, wherein the alloy blocking layer 2600 comprises AlN, AlGaN, InAlN, or InAlGaN. 29. The method of examples 21 and 27, wherein the III-nitride layer on the top and the sidewalls 1916 comprises an Mg diffused p-GaN layer 1918 having sidewalls and the height or thickness of the sidewalls 1916 is engineered to avoid direct hole injection into the n-side of the junction. 30. The method of example 29, wherein a temperature at which the Mg diffusion is performed is controlled to obtain different diffusion depths. 31. The method of any of the preceding examples, wherein volumetric hole injection is obtained for all the QWs of the active region of the device, due to the formation of p-type material at the sidewalls of the 3D engineered structures. 32. The method of any of the preceding examples, wherein: the light emitting device comprises a micro LED, and the 3D engineered structures reduce the size-dependent efficiency drop of the micro-LEDs in a micro-pixel display or visible light communication system. 33. The method of any of the preceding examples, further comprising selecting a larger number of QWs in the active region 1908 of the device so as to increase a volume of the active region and enhance or tailor efficiency and reduce current droop of the LED or laser. 34. The method of any of the preceding examples, wherein the 3D engineered structures each include a mesa, the method further comprising shaping the mesa and top metal contact to the mesa to increase light emission directionality from the 3D engineered structures. 35. The method of any of the preceding examples, wherein the 3D engineered structures are formed as a top-down or bottom-up light emitting structure. 36. The method of any of the preceding examples, wherein the 3D engineered structures comprise bottom-up core-shell or non-core-shell geometry light emitting structures. 37. The method of any of the preceding examples, further comprising selecting the composition of the active region 1908 so as to obtain the LED or laser emitting electromagnetic radiation having any visible wavelength. 38. The method of any of the preceding examples, further comprising: growing the active region 1908 of the LED or laser comprising a stack of QWs, each of the QWs configured to emit electromagnetic radiation having one of a red wavelength, a blue wavelength, a green wavelength, and a yellow wavelength; and wherein the stack is laterally injected with holes. 39. The method of any of the preceding examples, wherein the LED or laser comprises a III-nitride LED or III-nitride laser. 40. The method of any of the preceding examples, wherein the 3D engineered structures comprise core-shell nanostructure-based light emitting structures. 41. The method of any of the preceding examples, wherein the 3D engineered structures comprise a III-V material. 42. The method of any of the preceding examples, wherein the 3D engineered structures comprise GaN-based top-down or bottom-up nanostructure lasers for photonics applications. 43. The method of any of the preceding examples, wherein the light emitting device comprises an LED or laser emitting ultraviolet light. 44. Figure 19(b) and Figure 20(c) illustrate a device 1900, comprising: an array of three dimensionally (3D) engineered structures 1904 each comprising an active region 1908 comprising III-V material and a plurality of QWs and QBs; and a vertical junction 1906a and a lateral junction 1906b with each of the 3D engineered structures, wherein: holes are injected into the QWs in the active region through the vertical junction and the lateral junction, and the QWs and/or the QBs are p-type doped. 45. The device of example 44, further comprising a p-type layer 1914 on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region. 46. The device of example 44, further comprising: an n-type III-V layer 1917 providing electrons to the quantum wells; a p-type layer 1918 on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the QWs on the sidewall so as to inject holes laterally into each of the QWs; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer 1910 between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer 1918 and the 3D engineered structures. 47. The device of example 44, further comprising the active region 1908 between an n-type region 1914 and a p-type region 1912, and an unintentionally doped (UID) layer 1910 between the p- and the n-regions. 48. The device of any of the examples 44-47, wherein the p-type layer comprises p-type dopants diffused from a dopant layer deposited on the p-type layer. 49. The device of any of the examples 44-48, wherein the III-V layer 1917 comprises GaN, the p-type layer 1918 comprises p-type GaN, the dopant layer 2402 comprises a Magnesium layer, and the p-type dopants comprise Magnesium. 50. Figure 26 illustrates the device of any of the examples 44-49, further comprising a hole blocking barrier layer 2600 or n-type delta doped layer 2600 between the n-type layer and the active region 1914 so as to prevent or reduce direct hole injection to the «-side 1914 of the junction with the active region.
51. The device of example 50, wherein the hole blocking layer comprises AIN, AlGaN, InAIN, or InAlGaN.
52. The device of examples 44-51, wherein the device comprises a laser or light emitting diode and the III-V material and III-V layer comprise Ill-nitride.
53. The device of examples 44-52, wherein the sidewalls 1916: are inclined at an angle 1524 of less than 45 degrees, or at an angle between
45 degrees and 60 degrees, with respect to a base 1530 of the 3D engineered structures so as to increase surface area contact of the quantum wells with the p-type layer.
54. The device of examples 44-53, wherein: the 3D engineered structures have the sidewalls 1916 forming a convex or concave geometry, and/or the sidewalls 1916 have a truncated triangular shape, or the 3D engineered structures comprise a pyramidal shape.
55. The device of examples 44-54, further comprising a UID layer 1910 below the MQW active region 1908, the UID layer 1910 comprising: a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN, or a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN.
56. The device of examples 44-56, wherein the QBs comprise delta doping or modulation doping with a variety of dopants including, but not limited to, Mg.
57. The device or method of any of the preceding examples, wherein the 3D engineered structures comprise core-shell nanostructures. 58. The device or method of any of the preceding examples, wherein the core-shell nanostructures have a larger active region volume reduce the effective carrier density and efficiency droop. 59. The device or method of examples 57 or 58, wherein the core-shell nanostructures are fabricated using the method of examples 21 or 22 to avoid direct Mg diffusion into the active QWs during the Mg diffusion process. 60. The device or method of any of the preceding examples, wherein the 3D engineered structures include an active region 1908 comprising InGaN/GaN or InGaN/InGaN QWs/QBs for visible emitters emitting visible light, or AlGaN/AlGaN QWS/QBs for ultraviolet emitters emitting ultraviolet electromagnetic radiation. 61. The device of examples 44-60 manufactured using the method of examples 2-43. Advantages and Improvements of section III embodiments Section III of the present disclosure describes an LED structure, where the active QWs are p-type doped, with doping either in the QWs, the quantum barriers (QBs) separating the QWs, or both (with either uniform or localized, so-called delta doping). The doping of QBs has the possible advantage of better QW material quality as doping is often associated with degraded materials performance in the regions with dopants. LEDs or lasers with p-type doped MQWs have been well studied in the AlInGaAs material system due to their high modulation bandwidth3–5. This often comes with diminished threshold current and quasi unchanged turn-on voltage. If p- doping of QWs were used in the usual geometry of contacting the extreme layers of the MQW layer stack of AlInGaN materials, the same issue of carrier inhomogeneous injection as in unintentionally doped MQW structures would occur due to the large energy discontinuities of the AlInGaN heterostructures, at variance with the small energy discontinuities of the AlInGaAs material system. However, if we employ a lateral p-GaN contacting method to the p-type QWs, we are able to inject all the stacked QWs simultaneously and with similar efficiencies. The advantages of the proposed LED structure designs include (i) low-droop GaN-based RGBY LEDs by volumetric hole injection, (ii) more design freedom for thick active regions with large number of QWs for high efficiency, (iii) improved efficiency of green LEDs and contribute to solve the green gap, (iv) may mitigate the size-dependent efficiency drop in micro-LEDs due to the reduced surface effects. The position of the junctions within the MQWs (determined by the Mg diffusion length) can be adjusted by the duration and temperature of the Gallide process, to optimize uniformity of carrier injection. Due to the elimination of the need for hole transport in such structures, the associated transport delays between the wells are removed. Therefore, the design proposed here could significantly improve the modulation bandwidth of the LEDs, which is essential for visible-light communications. The shape of the mesa structure can be designed so that the light emitted sideways is redirected by the metal contact to increase the source brightness. An engineered large number of QWs for all wavelengths can be used in the active region without the issues with hole injections in the deeper wells. In particular, white LEDs on a single wafer can be obtained by designing active RGBY QWs with different emission colors on a single structure on a single chip. The white LED processed using this method has the advantage of higher efficiency compared to any phosphor-converted white LEDs (with slow and inefficient phosphor conversion process) and can be used in solid-state lighting as well as visible-light communications. In addition, it provides a better color-rendering index (providing sharper colors) compared to conventional phosphor converted white LEDs. Active region designs such as InGaN/GaN or InGaN/InGaN QWs/QBs for visible emitters emitting visible light, or AlGaN/GaN or AlGaN/AlGaN QWS/QBs for ultraviolet emitters emitting ultraviolet electromagnetic radiation can be considered. This method can be similarly applied to other III-nitride light emitting structures such as UV LEDs, and lasers. Commercial advantages of the method include: 1. Improved efficiency of LEDs at high applied current density for high- power LEDs: lower droop LEDs can be obtained. 2. As carrier density in the top QWs is diminished, thermal droop due to thermal carrier escape is diminished. 3. Implementation with industrially viable MOCVD growth. The method can be applied in the production line of any lighting companies. 4. This method can be applied to all wavelength LEDs and lasers. 5. Due to the deep hole injections, even white LEDs can be developed using the methods described herein. The white LED would be more efficient (with also higher color-rendering index) than conventional phosphor converted blue LEDs for solid state lighting. 6. The white LEDs developed by this method would provide higher modulation bandwidth compared to conventional phosphor converted blue LEDs for visible-light communication. 7. Due to the very high volume injection and improved efficiency, ultraviolet to infrared LEDs for high power applications can be obtained. References for section III The following references are incorporated by reference herein. 1 J. Cho, E.F. Schubert, and J.K. Kim, Laser Photonics Rev.7, 408 (2013). 2 J. Iveland, L. Martinelli, J. Peretti, J.S. Speck, and C. Weisbuch, Phys. Rev. Lett. 110, 177406 (2013). 3 K. Uomi, T. Mishima, and N. Chinone, Jpn. J. Appl. Phys.29, 88 (1990). 4 A. Schonfelder, S. Weisser, J.D. Ralston, and J. Rosenzweig, IEEE Photonics Technol. Lett.6, 891 (1994). 5 Y. Zheng, Highly-Strained P-Type Modulation Doped Active Regions for High- Speed VCSELs, D.Eng., University of California, Santa Barbara, 2012. 6 F. Zhang, N. Can, S. Hafiz, M. Monavarian, S. Das, V. Avrutin, Ü. Özgür, and H. Morkoç, Appl. Phys. Lett.106, 181105 (2015). 7 D. Li, editor , in Encycl. Microfluid. Nanofluidics (Springer US, Boston, MA, 2008), pp.1642–1643. 8 M. Nami, A. Rashidi, M. Monavarian, S. Mishkat-Ul-Masabih, Ashwin.K. Rishinaramangalam, S.R.J. Brueck, and D. Feezell, ACS Photonics 6, 1618 (2019). 9 M. Nami, I.E. Stricklin, K.M. DaVico, S. Mishkat-Ul-Masabih, A.K. Rishinaramangalam, S.R.J. Brueck, I. Brener, and D.F. Feezell, Sci. Rep.8, 501 (2018). Conclusion This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS 1. A device, comprising: a III-V light-emitting diode (LED) or III-V laser comprising intentional V- defects and a planar hole waveguide.
2. The device of claim 1, wherein the III-V LED or III-V laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises an alloy barrier interlayer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region.
3. The device claim 2, wherein a thickness and composition of the alloy barrier interlayer forms a barrier suppressing transfer of the holes into the quantum wells, increasing hole lateral hole diffusion in the QBs until the holes are captured by the QW via tunneling or percolative transport through the alloy barrier interlayer.
4. The device of claim 2, wherein one or more of the repeat units comprise another alloy barrier interlayer on another side of the QB to improve waveguiding of the holes.
5. The device of claim 1, wherein the LED or laser comprises: an active region including one or more repeat units including a quantum well (QW) on or adjacent to a quantum barrier (QB); and in one or more of the repeat units, the planar hole waveguide comprises a delta-doped layer in the QB to enhance a hole lateral diffusion length that increases or enables volumetric injection of holes into the active region.
6. The device of claim 5, wherein: the delta-doped layer comprises a doping at an interface between the QW and the QB, and a band-bending associated with the doping provides a barrier to injection of holes into the QW, leading to a longer lateral diffusion of the holes in QBs before being captured by the QWs.
7. The device of claim 5, wherein one or more of the repeat units include another delta-doped layer on another side of the QB to improve waveguiding of the holes.
8. The device of any of the claims 5-6, wherein the delta doped layer comprises a silicon (Si) delta doped III-nitride layer or GaN layer or a germanium (Ge) doped GaN or III-nitride layer.
9. The device of any of the preceding claims 1-8, further comprising: the active region comprising multi quantum wells, an n-type layer for providing electrons to the active region; and an unintentionally doped or n-type doped AlGaN layer between the n-type layer and the active region.
10. The device of any of the claims 1-9, wherein the V-defects comprise V-shaped lateral injectors comprising a superlattice structure coupled to the quantum wells in the active region.
11. The device of claim 10, wherein the V-shaped lateral injectors comprise V-shaped features on a patterned dielectric or a metal mask.
12. The device of any of the claims 1-11, wherein the LED or laser comprises a III-nitride LED or III-nitride laser.
13. A device, comprising: an array of three dimensionally (3D) engineered structures each comprising an active region comprising III-V material and a plurality of quantum wells; and a vertical junction and a lateral junction with each of the 3D engineered structures, wherein holes are injected into the quantum wells in the active region through the vertical junction and the lateral junction.
14. The device of claim 13, further comprising a p-type layer on or above a top and sidewall of each of the 3D engineered structures, the p-type layer forming the vertical junction comprising a p-type vertical junction and the lateral junction comprising a p-type junction with the active region.
15. The device of claim 13, further comprising: an n-type III-V layer providing electrons to the quantum wells; a p-type layer on a top and a sidewall of each of the 3D engineered structures, wherein the p-type layer is in contact with each of the plurality of the quantum wells on the sidewall so as to inject holes laterally into each of the quantum wells; and wherein the 3D engineered structures emit electromagnetic radiation when the holes recombine with the electrons in the active region; and a III-V layer between the n-type III-V layer and the 3D engineered structures and/or between the p-type layer and the 3D engineered structures.
16. The device of claim 15, wherein the p-type layer comprises p-type dopants diffused from a dopant layer deposited on the p-type layer.
17. The device of claim 15, wherein the III-V layer comprises GaN, the p- type layer comprises p-type GaN, the dopant layer comprises a Magnesium layer, and the p-type dopants comprise Magnesium.
18. The device of any of the claims 13-17, further comprising a hole blocking barrier layer between the n-type layer and the active region so as to prevent or reduce direct hole injection to the n-side of the junction with the active region.
19. The device of claim 18, wherein the hole blocking layer comprises AlGaN, InAlN, or InAlGaN.
20. The device of claim 18, wherein the hole blocking layer comprises an n-type delta doped III-V layer.
21. The device of any of the claims 13-20, wherein the device comprises a laser or light emitting diode and the III-V material and III-V layer comprise III-nitride.
22. The device of any of the claims 14-21, wherein the sidewalls: are inclined at an angle of less than 45 degrees, or at an angle between 45 degrees and 60 degrees, with respect to a base of the 3D engineered structures so as to increase surface area contact of the quantum wells with the p-type layer.
23. The device of any of the claims 13-22, wherein the 3D engineered structures have the sidewalls forming a convex or concave geometry.
24. The device of any of the claims 13-23, wherein the sidewalls have a truncated triangular shape, or the 3D engineered structures comprise a pyramidal shape.
25. The device of any of the claims 13-24, wherein the active region comprises a plurality of QWs and QBs and the QWs and/or the QBs are p-ty pe doped.
26. The device of any of the claims 13-25, further comprising an unintentionally doped (UID) layer below the active region comprising multi quantum wells, the UID layer comprising: a superlattice to improve material quality and carrier injection, the superlattice having a lower energy gap than GaN, or a graded InGaN layer, starting from pure GaN at the bottom to improve carrier injection, the graded InGaN layer having progressively lower energy gap than GaN.
27. The device of any of the claims 25-26, wherein the QBs comprise delta doping or modulation doping.
28. The device of any of the claims 13-27, wherein the 3D engineered structures comprise core-shell nanostructures.
29. The device of claim 28, wherein the core-shell nanostructures have a larger active region volume so as to reduce an effective carrier density and efficiency droop.
30. The device of any of the preceding claims 1-29, wherein the device comprises a hetero- and/or homo-junction GaN-based nano laser or LED for photonics and/or nanometrology applications.
31. The device of any of the claims 1-30, wherein the device comprises a nanolaser or nano LED comprises a Ill-nitride nanowire LED or a nanowire laser useful as a building block in a photonic integrated circuits (PIC) or as a light source.
32. The device of any of the claims 13-31, wherein the device is a light emitting device, a solar cell, a detector, or a transistor.
33. The device of any of the claims 1-27, wherein the device comprises a planar or a core shell structure, the core shell comprising the p-type layer forming a shell on a core comprising the active region, the device formed using a top-down or bottom-up geometry.
34. The device of one or more of the preceding claims 13-33, wherein the device comprises a transistor useful in a power electronics application.
35. A device useful in a power electronics application, comprising: an array of three dimensionally (3D) engineered structures each comprising III-V material and a p-n junction between a p-type layer and an n-type layer; the p-n junction comprising a vertical junction and a lateral junction, wherein holes are injected through the vertical junction and the lateral junction.
PCT/US2020/051264 2019-09-18 2020-09-17 Methods of hole injection in indium aluminum gallium nitride light-emitting diodes WO2021055599A1 (en)

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