WO2022248301A1 - Optoelektronisches bauelement und laser - Google Patents
Optoelektronisches bauelement und laser Download PDFInfo
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- WO2022248301A1 WO2022248301A1 PCT/EP2022/063415 EP2022063415W WO2022248301A1 WO 2022248301 A1 WO2022248301 A1 WO 2022248301A1 EP 2022063415 W EP2022063415 W EP 2022063415W WO 2022248301 A1 WO2022248301 A1 WO 2022248301A1
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- photonic crystal
- layer
- gain medium
- optoelectronic component
- quantum well
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- 230000005693 optoelectronics Effects 0.000 title claims abstract description 78
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/11—Comprising a photonic bandgap structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/185—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/2004—Confining in the direction perpendicular to the layer structure
- H01S5/2018—Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
- H01S5/2027—Reflecting region or layer, parallel to the active layer, e.g. to modify propagation of the mode in the laser or to influence transverse modes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/305—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
- H01S5/3095—Tunnel junction
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S2301/00—Functional characteristics
- H01S2301/16—Semiconductor lasers with special structural design to influence the modes, e.g. specific multimode
- H01S2301/166—Single transverse or lateral mode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S2301/00—Functional characteristics
- H01S2301/18—Semiconductor lasers with special structural design for influencing the near- or far-field
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
- H01S5/04254—Electrodes, e.g. characterised by the structure characterised by the shape
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/34333—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
Definitions
- semiconductor lasers Due to their small size and power spectrum, semiconductor lasers are used in a wide range of applications, for example in integrated sensor solutions.
- Semiconductor lasers can generally be divided into two classes: edge-emitting lasers, in which the laser light propagates parallel to the wafer surface of the semiconductor chip and is reflected or decoupled at a split edge, and surface-emitting lasers Lasers) in which the light propagates perpendicularly to the semiconductor wafer surface.
- a previously less common category of surface-emitting lasers is set up so that laser light propagates essentially in a cavity along the wafer surface (English: in-plane laser).
- a realization of this type of laser is the surface-emitting photonic crystal laser (English: Photonic Crystal Surface-Emitting Laser, abbreviated: PCSEL), in which a laser resonator lying in one plane is realized with a photonic crystal structure.
- PCSEL Photonic Crystal Surface-Emitting Laser
- the same structure also reflects part of the light to form the output beam.
- Single-frequency operation can be achieved here, which can be important for applications in 3D sensors and optical data transmission, for example.
- Surface-emitting photonic crystal lasers, or PCSELs can be realized, for example, by stacking functional layers.
- the lasers can and should have coupled waveguides in order to simplify production and adjust the laser characteristics for the respective application. At the same time, there is a need for high-quality components such as the photonic crystals used.
- One object is to specify an optoelectronic component and a laser that allow simpler production and improved laser characteristics.
- an optoelectronic component comprises a stack arrangement which has a photonic crystal and a gain medium.
- the gain medium comprises a layer sequence of at least two quantum wells and at least one tunnel diode (tunnel junction).
- the stack arrangement is arranged on a substrate which is transparent in the area of an electromagnetic wave to be emitted.
- the gain medium is configured to emit the electromagnetic wave.
- the photonic crystal is electromagnetically coupled to the gain medium.
- waveguides can, and often should, also be coupled. This saves, for example, a photonic crystal layer for each waveguide.
- the stacks can be arranged within a superwaveguide.
- the tunnel diodes With the help of the tunnel diodes, the individual quantum wells can be coupled coherently at a small spatial distance. Since only one layer with a photonic crystal is required in this concept, the production is also simplified, since nanostructuring only has to take place after the quantum wells and the tunnel diodes have been deposited and thus no additional defects are caused in the most sensitive layers of the component.
- an optoelectronic device in one embodiment, includes a stacked arrangement having a photonic crystal and a gain medium.
- the gain medium includes at least one quantum well and is configured to emit an electromagnetic wave.
- the photonic crystal is structured in a dielectric layer and electromagnetically coupled to the gain medium.
- the stacked arrangement is arranged on a substrate.
- the substrate can be transparent in the area of the electromagnetic wave, for example in order to couple out the electromagnetic wave. Alternatively can the substrate can be opaque in the area of the electromagnetic wave if, for example, it is not coupled out through this side.
- the photonic crystal cannot be structured directly into the semiconductor material, but in an additionally inserted layer that is close to the active zone.
- This layer comprises dielectric material, for example in combination with another dielectric material and/or a transparent conductive material such as indium tin oxide (ITO).
- ITO indium tin oxide
- materials with good optical properties and at the same time high thermal conductivity are suitable as dielectric materials, while other dielectric materials with less good thermal properties are also suitable in principle.
- An advantage of this approach over alternative concepts is that only a relatively thin layer of semiconductor material is required. As a result, the corresponding epitaxial process takes significantly less time and thus allows a cost-effective component with a comparatively simpler Architecture. By structuring in dielectrics, defects in the semiconductor can be reduced or even avoided.
- an optoelectronic device in one embodiment, includes a stacked arrangement having a photonic crystal and a gain medium.
- the gain medium includes at least one quantum well and is configured to emit an electromagnetic wave.
- the photonic crystal is patterned in a conductive layer and electromagnetically coupled to the gain medium.
- the stacked arrangement is arranged on a substrate.
- the substrate can be transparent in the area of the electromagnetic wave, for example in order to couple out the electromagnetic wave.
- the substrate can be opaque in the area of the electromagnetic wave if, for example, there is no outcoupling through this side.
- the implementation within the conductive layer, which has ITO, for example, on the p-side enables, for example, completely planarized structures that facilitate decoupling via the p-side (AR coating)—and allows thermal connection via the n-side.
- the layer sequence comprises the at least two quantum wells and the at least one tunnel diode. Furthermore, the photonic crystal is structured in the electrical layer.
- the photonic crystal is from Gain medium comprises such that the photonic crystal is arranged in the layer sequence.
- Gain medium may be arranged separately such that the photonic crystal is arranged on an outer layer of the layer sequence.
- the gain medium includes one or more constraining layers.
- the one or more confinement layer is arranged in the layer sequence such that a quantum well is spaced apart from a tunnel diode.
- a distance between the quantum well and the tunnel diode is set in such a way that a fundamental mode can be coupled out of the gain medium.
- the one or more confinement layers are spaced such that a space is set between the quantum well and the tunnel diode such that a plurality of individual modes can be coupled out of the gain medium and the individual modes are coupled by energy transfer.
- the photonic crystal includes a confinement layer.
- the dielectric layer includes a first dielectric material.
- the dielectric layer further comprises a second dielectric material and/or a conductive material that is transparent in the electromagnetic wave range.
- the conductive layer comprises a first conductive material, a second conductive material and/or a dielectric material that is transparent in the range of electromagnetic waves.
- the conductive layer and the dielectric layer can be combined by appropriate choice of material.
- a partially dielectric and partially conductive layer can be provided in this way.
- a photonic crystal structure of the photonic crystal comprises the first dielectric material and is completely embedded in the second dielectric material and/or the transparent conductive material.
- the photonic crystal structure of the photonic crystal may not be embedded in the second dielectric material and/or the transparent conductive material at least partially on a side facing a quantum well.
- a photonic crystal structure of the photonic crystal is in direct contact with the gain medium.
- the photonic crystal is patterned into a layer with no conductive material.
- a laser comprises one or more of the optoelectronic components according to the concept described here. Furthermore, a pump source provided and arranged for exciting stimulated emission by means of the gain medium.
- a method for producing an optoelectronic component comprises the following steps. First, a photonic crystal and a gain medium are arranged in a stacked arrangement. The stack arrangement is also arranged on a substrate which is transparent in the area of an electromagnetic wave to be emitted.
- the gain medium comprises at least two quantum wells and at least one tunnel diode in a layer sequence. The gain medium is configured to emit the electromagnetic wave. Finally, the photonic crystal is electromagnetically coupled to the gain medium.
- a method for producing an optoelectronic component comprises the following steps. First, a photonic crystal and a gain medium are arranged in a stacked arrangement. The stack arrangement is arranged on a substrate which is transparent in the area of an electromagnetic wave to be emitted. The gain medium includes at least one quantum well and is configured to emit the electromagnetic wave. The photonic crystal is structured in a dielectric layer and electromagnetically coupled to the gain medium.
- FIGS. 1 to 16 examples of optoelectronic components.
- FIG. 1 shows an example of an optoelectronic component.
- the optoelectronic component comprises a stack arrangement, which has a photonic crystal 1 and a gain medium 3 .
- the photonic crystal 1 consists, for example, of a thin layer of semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent to an electromagnetic wave to be emitted, ie is not or only slightly absorbing.
- the electromagnetic wave to be emitted lies, for example, in the infrared, IR, ultraviolet, UV, or in the visible, VIS, part of the electromagnetic spectrum.
- the photonic crystal 1 comprises a photonic structure 11, which represents a periodic structure of the refractive index and makes it possible to guide, filter and/or reflect wavelength-selectively electromagnetic waves through optical processes such as diffraction and interference.
- the periodic photonic structure determines or defines, for example, the direction of emission, wavelength and divergence of the electromagnetic wave that can be emitted with the optoelectronic component.
- the photonic crystal structure 11 comprises one or two dimensionally arranged structure elements 12 arranged in a pattern (e.g. a square or triangular pattern) so as to form the photonic crystal structure extending over a certain direction or area.
- the structural elements may include air holes or dielectric material.
- As a two-dimensional photonic crystal structure it functions as a kind of lateral cavity.
- the photonic structure is characterized by the distance (pitch) between the structural elements or their fill factors and other parameters.
- the expansion of the photonic crystal in one plane is not shown in the drawing, so that a two-dimensional distribution of the periodic photonic structure results.
- the photonic crystal can extend along one direction, resulting in a one-dimensional distribution of the periodic photonic structure.
- the amplification medium 3 comprises a layer sequence of quantum wells 30 (quantum wells), tunnel diodes 31 (tunnel junction) and delimitation layers 32 (cladding).
- the quantum wells are an active medium and are set up to emit the electromagnetic wave by stimulated emission when suitably excited.
- the gain medium is delimited by two outer confinement layers.
- the photonic crystal is a first outer confinement layer for the gain medium.
- a second outer confinement layer 33 confines the gain medium from a substrate 5 on which the stacked assembly is disposed.
- the substrate is transparent in the electromagnetic wave range.
- the The first and second outer constraining layers may have a different layer thickness than the constraining layers 32 of the gain medium.
- the stacked arrangement of gain medium forms a common waveguide bounded by the first and second outer confinement layers.
- the confinement layers 32 of the gain medium have equal thicknesses in this example.
- the layer thicknesses are between 100 nm and 500 nm.
- the delimitation layers have a doped semiconductor and are, for example, n- or p-doped.
- the stacked arrangement comprises a plurality of quantum wells, three in this example, but at least two quantum wells.
- This structure is known in English as a multi-quantum well.
- the first quantum well is photonically coupled to the photonic crystal.
- the photonic crystal is placed on the first quantum well.
- photonically coupled refers to this spatial proximity, which during operation of the optoelectronic crystal (for example in a laser) leads to an evanescent field being formed between the photonic crystal and the quantum well. This will be explained in more detail below.
- the first quantum well is followed by a further confinement layer 32, followed by a first tunnel diode 31 and a further confinement layer 32.
- This sequence is repeated for a second quantum well 30 with a further confinement layer 32, followed by a second tunnel diode 31 and a further confinement layer 32.
- This delimitation layer is followed by a third quantum well 30, which to a certain extent closes off the stack arrangement in the direction of the substrate 5.
- the third Quantum well 30 is arranged on the second outer confinement layer 33 .
- the tunnel diodes 31 represent pn transitions, for example.
- An advantageous sequence of n- and p-doped regions can thus be set by the layer sequence.
- the sequence of the respective quantum well, confinement layer and tunnel diode ensures that only one fundamental mode per quantum well is established with suitable excitation.
- a "super" fundamental mode is created by superimposition, which is determined by layer thicknesses and the relative position of the quantum wells. It has been found that layer thicknesses of less than 1 pm are advantageous for this, with a layer thickness describes a sequence of the respective quantum well, confinement layer and tunnel diode.
- the quantum wells are so close together that the quantum wells are photonically coupled to one another and the "super" fundamental mode is established.
- the position of the tunnel diodes in the stack arrangement has turned out to be less critical because the fundamental modes have no nodes, etc.
- Laser amplification by stimulated emission can thus be achieved by coupling the photonic crystal structure to the thin active layers (quantum wells) beneath the photonic crystal layer within the evanescent fields corresponding to the fundamental modes.
- the substrate includes two opposing surfaces.
- a surface 51 is provided with the outer confinement layer 33 so that the layer sequence is arranged on the substrate.
- the opposite surface 52 is optionally provided with a reflective layer 53 .
- This reflection layer has, for example, a (metal) Reflector or a Bragg mirror (English: Bragg Mirror) on.
- the reflective layer can also be provided on the surface 51 .
- the reflection layer is optional because it is not part of the resonator or high reflectivity on the substrate is not absolutely necessary for laser activity.
- the optoelectronic component can be operated as part of a laser.
- a suitable pump source electrical or optical, induces stimulated emission in the gain medium.
- an electric current for pumping the active region ie the quantum wells
- metallic electrodes on the top and bottom of the optoelectronic component, for example on the photonic crystal and the opposite surface 52 of the substrate.
- the electrodes are not shown in the drawing.
- the laser emission is from the top (indicated by an arrow) where the photonic crystal is located.
- the electrode covers only a small part of a radiating surface, for example a rectangular area with dimensions of the order of 10 gm to 100 gm. It is also possible to use a top electrode from which a rectangular area in the center has been removed. This leads to pumping of the photonic crystal mode in its outer region, while output coupling is possible in the central region.
- the laser amplification by stimulated emission is achieved by coupling the photonic crystal structure 11 of the photonic crystal 1 with the quantum wells 30 of the gain medium as an active layer (amplifier layer) below the photonic crystal layer 11 within the evanescent fields of the modes.
- the boundary layers set a distance between a quantum well and a tunnel diode in such a way that a fundamental mode can be coupled out of the gain medium.
- the active regions are separated from the photonic structure in the layer sequence in order to keep the electrical charge carriers confined in the active region, but are photonically coupled thereto by means of the confinement layer 32 and tunnel diode 31 sequence.
- the optically transparent and electrically conductive cladding layer made of doped semiconductor (outer boundary layer 33 and photonic crystal 1) is located above and below the stack arrangement.
- the sequence of the respective quantum well, confinement layer and tunnel diode leads to a fundamental mode being established for each quantum well.
- a “super” fundamental mode is created by superimposition, which is determined by layer thicknesses and the relative position of the quantum wells.
- the reflection layer 53 for example a Bragg reflector (Bragg mirror). one side of the stack, more efficient power extraction can be achieved.
- the waveguides By coupling the waveguides, large-area lasers with high power density can be generated with only diffractively limited beam collimation.
- the optoelectronic components can be arranged within a super waveguide.
- the individual quantum wells can be coherently coupled with a small spatial distance by means of the tunnel diodes. Since only one layer with a photonic crystal is required in this concept, production is also made easier because nanostructuring can only take place after the quantum wells and the tunnel diodes have been deposited and thus no additional defects are caused in the most sensitive layers of the component.
- FIG. 2 shows a further example of an optoelectronic component.
- the optoelectronic component is based on the previous example and has only been changed in the following features compared to FIG.
- the reflection layer 53 is now arranged on an outer surface 12 of the photonic crystal.
- This reflection layer has, for example, a (metal) reflector or a Bragg mirror and is optional because it is not part of the resonator or high reflectivity is not absolutely necessary for laser activity.
- An anti-reflection layer 54 (anti-reflection coating) can be applied to the surface 52 of the substrate in order to support the decoupling of laser light in the direction of the substrate 5 . In this example, laser emission takes place along the underside of the component (indicated by an arrow), i.e. in the direction of substrate 5.
- FIG. 3 shows a further example of an optoelectronic component.
- the optoelectronic component is also a further development of the example from FIG. 1 and has only been changed in the following features.
- the gain medium 3 comprises a different layer sequence than that described in FIG.
- a first quantum well is followed by a confinement layer 32, followed by a tunnel diode 31.
- a further delimitation layer 32 follows.
- This delimitation layer is followed by a second quantum well 30 which to a certain extent completes the layer sequence in the direction of the substrate 5 .
- no third quantum well is provided. Instead, the second quantum well is closed off by an outer confinement layer 33 .
- the photonic crystal 1 represents another outer boundary layer.
- the boundary layers 32 each have a different layer thickness than the tunnel diode 31 or the quantum wells 30.
- the layer thickness of the boundary layers 32 is selected such that a distance between a quantum well and the tunnel diode is set in such a way that several individual modes from the Gain medium can be decoupled. Due to the distance chosen, the individual modes are coupled by energy transfer.
- Laser amplification by stimulated emission is achieved by coupling the photonic crystal structure 11 of the photonic crystal 1 with the quantum wells 30 of the gain medium as the active layer (amplifier layer) below the photonic crystal layer 11 within the evanescent fields of the modes.
- the confinement layers each adjust a distance between a quantum well and the tunnel diode so that the gain medium is divided into two waveguides each forming a single mode.
- the active regions are separated from the photonic structure in the layer sequence in order to keep the electrical charge carriers confined in the active region, but are photonically coupled thereto by means of the confinement layer 32 and tunnel diode 31 sequence.
- Above and below the layer sequence is the optically transparent and electrically conductive cladding layer made of doped semiconductor (outer boundary layer 33 and photonic crystal 1).
- the sequence of quantum well, confinement layer and tunnel diode leads to a single mode being established for each quantum well or waveguide.
- the thickness of the quantum wells (multi-quantum well), tunnel diode and confinement layers it is possible to ensure that the waveguides are coherently coupled.
- the individual modes that arise overlap and exchange energy through coupling. This allows laser light to be extracted from a central photonic crystal.
- FIG. 4 shows a further example of an optoelectronic component.
- the optoelectronic component is based on the previous example and has only been changed in the following features compared to FIG.
- the reflection layer 53 is now arranged on an outer surface 12 of the photonic crystal.
- This reflection layer has, for example, a (metal) reflector or a Bragg mirror and is optional because it is not part of the resonator or high reflectivity is not absolutely necessary for laser activity.
- An anti-reflection layer 54 (anti-reflection coating) can be applied to the surface 52 of the substrate in order to support the decoupling of laser light in the direction of the substrate 5 .
- laser emission takes place along the underside of the component (indicated by an arrow) in the direction of the substrate 5.
- FIG. 5 shows a further example of an optoelectronic component.
- the photonic crystal is arranged in the layer sequence.
- the photonic crystal can also lie between the waveguides, for example within the tunnel diode or in an intermediate boundary layer 32 (English: cladding). Thin, low-loss tunnel diodes can be beneficial.
- the photonic crystal structures can also be on the substrate side. The emission direction, wavelength and divergence are also determined or defined by the structure of the photonic crystal (pitch, fill factor, etc.).
- FIG. 6 shows a further example of an optoelectronic component.
- the optoelectronic component comprises a stack arrangement which has a photonic crystal 1 and a gain medium 3 .
- the gain medium includes a quantum well 30, which is set up as an active medium to emit an electromagnetic wave.
- the gain medium is arranged on a transparent substrate 5 .
- the substrate has a semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent to the electromagnetic wave to be emitted, ie is not or only slightly absorbent.
- the electromagnetic wave to be emitted lies, for example, in the infrared, IR, ultraviolet, UV, or in the visible, VIS, part of the electromagnetic spectrum.
- An anti-reflection layer 54 (anti-reflection coating) is applied to a surface 52 of the substrate in order to support the decoupling of laser light in the direction of the substrate 5 .
- an electrode 53 for example an n-contact, is arranged on the surface 52.
- laser emission occurs along the bottom (indicated by an arrow).
- the electrode is designed to cover only a small part of the surface 53, for example a rectangular area with dimensions of the order of 10 gm to 100 gm. It is also possible to use an electrode where a rectangular area is in the center has been removed.
- the amplification medium is arranged with a layer sequence on a further surface 51 of the substrate opposite the surface 52 .
- the layer sequence includes differently doped semiconductors which enclose a quantum well 30 .
- a first semiconductor layer 34 of n-doped GaN is disposed on the surface 51, followed by a quantum well 30.
- a second semiconductor layer 34 of p-doped GaN is disposed on top of the quantum well.
- the configuration of the amplification medium in particular the layer sequence, can be replaced or expanded by one from FIGS. 1 to 5, it being possible for the semiconductor layers 34 to be replaced or supplemented by delimiting layers. In this way, the exemplary embodiments of FIGS. 1 to 5 can be exchanged or supplemented with those of FIGS.
- the photonic crystal 1 is structured in a dielectric layer 14 and electromagnetically coupled to the gain medium.
- the dielectric layer 14 comprises a first layer 15 which has a first dielectric material, in this example ITO.
- the photonic structure 11 is structured into a second layer 16, which also comprises the first dielectric material.
- the structural elements 13 have a second dielectric material.
- the dielectric layer 14 further includes a third layer 17 which makes contact with the gain medium.
- Dielectric layer 14 includes dielectric material in combination with another dielectric material and/or a transparent conductive material, such as indium tin oxide (ITO for short).
- ITO indium tin oxide
- materials with good optical properties and, at the same time, high thermal conductivity are suitable as dielectric materials, while other dielectric materials with less good thermal properties are also suitable in principle, but may have other disadvantages.
- ITO can be mixed with TCO, with TCO denoting transparent, electrically conductive oxides (English: Transparent Conducting Oxides, TCO).
- TCO transparent Conducting Oxides
- the refractive indices given below can be used.
- a second electrode 18, for example a p-contact, is also arranged on the photonic crystal.
- the electrode comprises, for example, a material (for example Au or Al) that is reflective of the electromagnetic radiation to be emitted.
- the electrode may be surrounded by an insulator configured in the form of an aperture 19 to provide a current opening.
- the optoelectronic component can be excited to stimulated emission and emission of the electromagnetic wave as laser radiation by means of the two electrodes.
- the photonic Structure made of a dielectric material completely embedded in a transparent conductive material, thus forming the photonic crystal.
- the layer thicknesses of p-GaN and the directly adjacent closed ITO layer are preferably very thin to ensure a small distance ( ⁇ 300 nm preferably ⁇ 100 nm to ⁇ 50 nm) of the photonic crystal from the quantum wells.
- FIG. 7 shows a further example of an optoelectronic component.
- the optoelectronic component corresponds to the example from FIG. 6, but this exemplary embodiment has an aperture 20 in addition to the photonic structure. This can consist directly of the same material system as the photonic crystal and/or of a different material such as metal.
- the aperture delimits, for example, the dielectric layer (e.g. layers 16, 17).
- Laser characteristics such as beam expansion or divergence advantageously affect.
- FIG. 8 shows a further example of an optoelectronic component.
- the optoelectronic component corresponds to the example from FIG. 6 with the difference that the dielectric layer 14 only comprises the first and second layer 15, 16 and no third layer 17. Instead, contact with the gain medium is made directly by means of the second layer 16.
- the distance between the photonic structure and the quantum wells is reduced even further by not providing a closed dielectric layer, for example an ITO layer, between the p-GaN and the photonic crystal. It is important here that good charge transport to the active zone can nevertheless take place. In this case, too, an aperture 19 can be structured on the photonic crystal or in it.
- FIG. 9 shows a further example of an optoelectronic component.
- the optoelectronic component is a continuation of FIG. 8 with the difference that the photonic crystal is structured in a dielectric layer 14 that has no conductive material.
- the dielectric layer includes two dielectric materials with different indices of refraction.
- an intermediate layer 35 is inserted in the layer sequence with very good transverse conductivity (for example p++GaN) between the photonic crystal 1 and the gain medium 3 .
- the dielectric layer 14 is embedded in the electrode.
- the electrode comprises a material (for example Au or Al) which is reflective of the electromagnetic radiation to be emitted.
- the electrode may be surrounded by an insulator designed in the form of a (current) aperture 19 to provide a current opening.
- the substrate 5 can also have a (current) aperture 19 and an electrode 55 , for example an n-contact, and an anti-reflection layer 54 on the surface 52 .
- FIG. 10 shows a further example of an optoelectronic component.
- the optoelectronic component is a further development of the exemplary embodiment in FIG. 9.
- the photonic crystal is structured by a combination of conductive material (for example TCO) and dielectrics deposited in two different processes.
- a TCOL film 21 is first deposited by means of, for example, ALD, which is deposited in the depths of the photonic crystal and makes contact with GaN p++ there.
- a planar TC02 film 22 is deposited, which closes the photonic crystals flat, but does not fill them up. The p-contact is thus realized via TC02 and TCOL on p-GaN.
- the dielectric layer 14 comprises the first layer 15 in which the structural elements 13 are embedded.
- the layer 15 and the structural elements are covered with the film 21.
- Film 22 forms a planar shutter on film 21.
- the optoelectronic component can be further developed.
- the photonic crystal structure is processed by molding a shape-retaining layer, such as silicon.
- the silicon is structured in the process.
- the dielectric is then deposited - it molds the silicon.
- the silicon is removed again (depending on the wavelength/absorption of Si at the wavelength, the silicon can remain).
- the further process can take place as described in FIG.
- an a.Si can also be used, for example are high refractive index. Due to the thin layer, the absorption in Si is justifiable even at, for example, 450 nm (for example, 80% transmission at 100 nm thickness at 450 nm). However, since the Si only occupies part of the photonic crystal, the transmission is significantly higher (filling factor). Compared to other dielectrics, a-Si has the advantage that it can be structured very precisely.
- the concept presented here is suitable for GaN-based PC VCSELs, but can also be used for GaAs- and InP-based systems. Especially since the advantages become clear here.
- a mirror can also be used on the substrate side.
- the exemplary embodiments can also be set up for coupling out laser emission via the upper side, with the metallization being adapted for this purpose, for example.
- FIG. 11 shows a further example of an optoelectronic component.
- the optoelectronic component includes a stack arrangement which has a photonic crystal and a gain medium.
- the gain medium includes a quantum well 30, which is set up as an active medium to emit an electromagnetic wave.
- the gain medium is arranged on a transparent substrate 5 .
- the substrate has a semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent to the electromagnetic wave to be emitted, ie is not or only slightly absorbing.
- the electromagnetic wave to be emitted lies, for example, in the infrared, IR, ultraviolet, UV, or in the visible, VIS, part of the electromagnetic spectrum.
- the gain medium comprises two semiconductor layers 34 .
- a first semiconductor layer is p-doped, for example, and a second semiconductor layer is n-doped.
- the second semiconductor layer faces the gain medium and is n-doped (e.g. nGaN) and the first semiconductor layer faces a conductive layer 21 and is p-doped (e.g. pGaN).
- Boundary layers can be replaced or supplemented. In this way, the exemplary embodiments shown can be exchanged or supplemented.
- a photonic crystal is patterned in the conductive layer 21 and electromagnetically coupled to the gain medium.
- the conductive layer 21 comprises a first layer 22 which has a first conductive material.
- This can be a TCO, "TCO" designating transparent, electrically conductive oxides (English: Transparent Conducting Oxides, TCO).
- the first conductive material is ITO.
- the first layer 22 is used for the lateral closure of the optoelectronic component.
- a photonic structure is patterned into a second layer 23, which also includes the first conductive material.
- the photonic structure is formed by structure elements 25 (English: voids).
- the structure elements are shown enlarged in the image on the right and are, for example, in the order of magnitude of the emission wavelength of the optoelectronic component, for example around 300 nm.
- the structuring of the second layer 23 and thus of the structure elements 25 is carried out, for example, by an edging process.
- the conductive layer 21 also includes a third layer 24 which establishes contact with the gain medium 3 .
- the third conductive layer 24 is planar on a surface of the gain medium.
- the conductive layer 21 or the layers 22, 23, 24 can be produced by different deposition methods, for example atomic layer deposition (ALD), sputtering methods or settings.
- a variant with overgrown or oversputtered voids 25 also has the advantage that the etched structures can originally be larger than they are ultimately required (since they partially grow over again during sputtering). This means there is more Freedom or other options regarding
- an anti-reflection coating can be applied to closed structures.
- FIG. 12 shows a further example of an optoelectronic component.
- the optoelectronic component in particular the conductive layer 21 from FIG. 11, can be structured by means of etching and masks. Structural elements 25 of different depths can be produced here.
- the drawing on the left shows a structuring that can be achieved by a combination of two lithography steps, each with a subsequent etching step.
- a gray lithography step and an etching step can be performed, allowing good alignment between sublattices.
- Both alternatives allow structures 26, 27 of different depths to be introduced into the second layer 23. These structures can then be formed by applying the second layer 23 alone and/or together with the first layer 22 and thus form the structural elements 25.
- the drawing on the right shows the structural elements formed as a result.
- the conductive material for example ITO, can be applied by sputtering and the structures 26, 27 encapsulate.
- the first layer 22 can also be applied in this step and finally planarized.
- FIG. 13 shows further examples of an optoelectronic component.
- the drawing on the left shows the optoelectronic component according to FIG. 11, electrical contacting also being shown.
- an electrode 53 On a surface 52 of the substrate is an electrode 53, for example an n-contact, arranged.
- an anti-reflection layer anti-reflection coating
- laser emission occurs along the underside 52.
- the electrode is designed to cover only a small portion of the surface 52, for example a rectangular area with dimensions of the order of 10 ⁇ m to 100 ⁇ m Use an electrode that has a rectangular area in the center removed. This leads to pumping of the photonic crystal mode in its outer region, while output coupling is possible in the central region.
- the electrode comprises, for example, a material (for example Au or Al) that is reflective of the electromagnetic radiation to be emitted.
- the second electrode 18 allows contacting from the rear.
- the first or second electrode may be comprised of an insulator configured in the form of an aperture 19 to provide a current opening.
- the electrode 18 is shown on the right side of the drawing. Instead of being on the surface 52 of the substrate, the electrode is arranged in the semiconductor layer 34 and next to the gain medium, for example in the second, n-doped semiconductor layer facing the gain medium.
- the second electrode 18 thus allows contact to be made from the front.
- the optoelectronic component can be excited to stimulated emission and emission of the electromagnetic wave as laser radiation by means of the two electrodes.
- the photonic structure made of a conductive material is completely embedded in a transparent conductive material and thus forms the photonic crystal.
- the electrodes are arranged in such a way that emission takes place on the substrate side via the aperture 19 of the first electrode.
- FIG. 14 shows further examples of an optoelectronic component.
- the drawing on the left shows the optoelectronic component according to FIG. 12 (left), a reflector 26, in particular an epi-DBR reflector, being additionally arranged on or in the substrate.
- the electrodes are set up so that emission occurs on top via the aperture 19 of the first electrode.
- FIG. 15 shows a further example of an optoelectronic component.
- This component corresponds to that according to FIG. 11, with the conductive layer 21 being open, ie no first layer 21 is provided for a lateral closure of the optoelectronic component.
- the structures 26, 27 remain without encapsulation and thus form the structural elements of the optoelectronic component.
- a current distribution can form laterally in the conductive layer 21, for example in intermediate webs of the ITO.
- FIG. 16 shows further examples of an optoelectronic component. These components correspond to those according to FIG. 15, one reflector each, in particular an epi-DBR reflector, being additionally arranged on or in the substrate.
- the priorities of the German patent applications DE 102021113598.2 and DE 102021128124.5 are claimed, the disclosure content of which is hereby expressly incorporated by reference.
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JP2023571209A JP2024519809A (ja) | 2021-05-26 | 2022-05-18 | 光電子構成要素及びレーザ |
DE112022001250.1T DE112022001250A5 (de) | 2021-05-26 | 2022-05-18 | Optoelektronisches bauelement und laser |
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DE102021113598.2 | 2021-05-26 | ||
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WO2020047828A1 (zh) * | 2018-09-07 | 2020-03-12 | 中国科学院半导体研究所 | 窄垂直远场发散角的隧道结光子晶体激光器 |
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- 2022-05-18 DE DE112022001250.1T patent/DE112022001250A5/de active Pending
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WO2020047828A1 (zh) * | 2018-09-07 | 2020-03-12 | 中国科学院半导体研究所 | 窄垂直远场发散角的隧道结光子晶体激光器 |
Non-Patent Citations (2)
Title |
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LIU SHIH-CHIA ET AL: "Electrically Pumped Hybrid III-V/Si Photonic Crystal Surface Emitting Lasers with Buried Tunnel-Junction", 2018 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), OSA, 13 May 2018 (2018-05-13), pages 1 - 2, XP033382246 * |
MARJANI SAEID ET AL: "Threshold characteristics analysis of InP-based PhC VCSEL with buried tunnel junction", 2013 21ST IRANIAN CONFERENCE ON ELECTRICAL ENGINEERING (ICEE), IEEE, 14 May 2013 (2013-05-14), pages 1 - 4, XP032483249, DOI: 10.1109/IRANIANCEE.2013.6599783 * |
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