Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/81—Bodies
  • H10H20/822—Materials of the light-emitting regions
  • H10H20/824—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP
  • H10H20/825—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP containing nitrogen, e.g. GaN
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/81—Bodies

Definitions

• the high-Al content Al x Ga y N layer permits electronic and optoelectronic devices to be manufactured that are uncompromised by migration or diffusion of dopant species (e.g., magnesium, silicon, etc.) into the active device region, during the high temperature fabrication steps involving in the manufacture of such electronic and optoelectronic devices, including epitaxial growth and device fabrication.
• dopant species e.g., magnesium, silicon, etc.
• dopants such as silicon and magnesium readily migrate or diffuse into active regions of the device structure during high temperature processing conditions such as metalorganic chemical vapor deposition (MOCVD) and post-deposition fabrication operations. Such transport of the dopant species into the active region is severely detrimental to the ultimate performance and efficiency of the Hi-nitride optoelectronic device.
• MOCVD metalorganic chemical vapor deposition
• post-deposition fabrication operations Such transport of the dopant species into the active region is severely detrimental to the ultimate performance and efficiency of the Hi-nitride optoelectronic device.
• the transport of dopant species into the active region of the optoelectronic device will reduce the luminous efficiency of the device due to formation of non-radiative centers, as well as radiative centers with undesirable wavelength characteristics (i.e., deviations from the desired emission wavelength), and the development of micro-morphological defects, which in turn substantially reduce the efficiency of the product device.
• the present invention relates to Hi-nitride electronic and optoelectronic devices, and methods of making same.
• a barrier layer being formed of a material comprising AlGaN having at least 50% Al, based on the total amount of Al and Ga, therein, whereby the AlGaN layer provides a barrier to migration or diffusion of dopant species from the doped ffl-nitride layer into the active region of the device.
• Yet another aspect of the invention relates to a method of forming a ffl-nitride optoelectronic device structure including an active region and a doped Ill-nitride layer overlying the active region, such method comprising forming an AlGaN layer intermediate the active region and doped ffl-nitride layer, to form a barrier layer for suppressing migration or diffusion of dopant from the doped ffl-nitride layer into the active region.
• the invention in another aspect, relates to a method of producing a highly doped region in a microelectronic device structure including a doped material and an active region material, such method comprising (i) forming an intermediate layer between the doped material and the active region material to produce an interfacial region of increased strain, in relation to a corresponding microelectronic device structure lacking such intermediate layer and wherein the doped material and active region material are contiguous to one another, and (ii) effecting transport of dopant from the doped material toward the active region material so that dopant is accumulated in such interfacial region of increased strain.
• Yet another aspect of the invention relates to a multiple quantum well UV LED structure including a Mg-doped p-AlGaN layer, an active region, and a magnesium diffusion barrier layer therebetween, wherein the magnesium diffusion barrier layer comprises A1N.
• FIG. 1 is a schematic representation of the layer structure of an ultraviolet 1 ight emitting diode (UV-LED) comprising successive layers of N- AlGaN, active region material and p-AlGaN on a substrate.
• UV-LED ultraviolet 1 ight emitting diode
• FIG. 2 is a schematic representation of the layer structure of a UV-LED structure similar to that of FIG. 1 , but utilizing an A1N barrier layer between the active region and p- AlGaN layer.
• FIG. 3 is a graph of concentration of magnesium and aluminum atoms as a function of depth in UV-LED samples, with and without the AIN barrier layer in respective comparative samples, as determined by secondary ion mass spectroscopy (SIMS), showing the effectiveness of the AIN barrier layer.
• SIMS secondary ion mass spectroscopy
• FIG. 4 is an energy band diagram of a (MQW) UV LED device structure with an AIN layer inserted between the active region and p-cladding layer of the structure.
• FIG. 5 is a graph of tunneling probability (%) as a function of AIN thickness in Angstroms, for different relative effective masses (mO) and hole energies (E).
• dopants e.g., Si, Mg, Be, Fe, Zn, O, Ge, etc.
• the Al x Ga y N barrier material has high Al concentration, comprising at least 50% and up to (and including) 100% Al concentration, based on total aluminum and gallium content.
• Such high Al content Al x Ga y N material has been discovered to effectively inhibit diffusion and migration of dopant species from doped layers into the active region of the ffl-N optoelectronic device structure. Barrier layers formed of such material are particularly effective in suppressing contamination of the active region by dopant species such as magnesium and silicon.
• the Al x Ga y N barrier in the broad practice of the invention is readily formed by any suitable thin film formation techniques, including vapor deposition techniques such as metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), etc., at appropriate process conditions therefore, as part of the process flow sequence for the manufacture of the product ffl-nitride optoelectronic device.
• MOCVD metalorganic chemical vapor deposition
• MBE molecular beam epitaxy
• HVPE hydride vapor phase epitaxy
• FIG. 1 is a schematic representation of the layer structure of an ultraviolet 1 ight emitting diode (UV-LED) structure 10 comprising successive layers of N- AlGaN 16, active region material 14 and p-AlGaN 12 on a substrate 18.
• the substrate 18 can be of any suitable type, e.g., sapphire, spinel, SiC, GaN, etc.
• Contacts can be placed on the backside layer 18 or layer 12 to form the contact elements for the device.
• FIG. 2 is a schematic representation of the layer structure of a UV-LED structure similar to that of FIG. 1, wherein the same layers are corresponding numbered but utilizing an AIN barrier layer 20 between the active region 14 and p-AlGaN layer 12 of the structure 10.
• FIG. 3 is a graph of concentration of magnesium and aluminum atoms as a function of depth in these UV-LED samples, with and without the AIN barrier layer in the respective comparative samples.
• the dopant analysis results shown in FIG. 3 were determined by secondary ion mass spectroscopy (SIMS), and show the effectiveness of the AIN barrier layer.
• SIMS secondary ion mass spectroscopy
• the magnesium area density in the active region of the device structure containing no AIN layer was 5.1 x 10 12 cm "2
• the magnesium area density in the active region of the corresponding device structure that included an AIN layer between the active region and p- AlGaN cladding was 1.5 x 10 12 cm "2 .
• the invention provides a migration/diffusion barrier layer that enables higher dopant densities to be implemented in doped materials of device structures without the attendant problems of dopant contamination in the active region of the device attributable to migration/diffusion of the dopant at elevated temperatures in the fabrication of the microelectronic device structure, such as are encountered in the conventional manufacture of optoelectronic devices lacking the barrier layer of the present invention.
• the barrier layer structure of the present invention enables ffl-nitride optoelectronic devices to be manufactured that have substantially improved device lifetimes, higher luminous efficiency and lower heat production in operation than are achievable in corresponding optoelectronic devices lacking the migration/diffusion barrier layer of the present invention.
• analysis of magnesium concentration revealed localized magnesium accumulation at the interface of the barrier layer and the p-AlGaN layer.
• interfacial region dopant accumulation behavior can be utilized to effect channel definition or to remove dopants from a layer without removing the associated charge contribution, as a technique for optimizing the performance of the optoelectronic device.
• the interfacial region dopant accumulation behavior of the dopant species can be utilized for introducing dopants into a layer in a positionally fixed manner.
• a Al x Ga y N migration/diffusion barrier layer in accordance with the present invention facilitates engineering of the device structure with respect to band structures of the ffl-nitride device (e.g., (Al,Ga,In)N and other nitride alloy devices, where (Al,Ga,In) represents any stoichiometrically appropriate nitrides whose metal moiety includes one or more of aluminum, gallium and aluminum).
• the use of an Al x Ga y N migration/diffusion barrier layer in accordance with the present invention also permits engineering of the tunneling probability of carriers in the impurity diffusion barrier layer.
• FIG. 4 A simplified depiction of a band diagram, without adjustment for piezoelectric effects, is shown in FIG. 4 for a multiple quantum well (MQW) UV LED structure having an AIN magnesium diffusion barrier layer between the p-AlGaN layer and the active region.
• MQW multiple quantum well
• equation (1) can be simplified as
• increasing the drive voltage of the device i.e., E), causes the tunneling probability to be substantially increased, by about 20% in the specific example considered.
• very low thickness of the barrier layer can be employed to prevent migration/diffusion of magnesium and other dopant species.
• the invention contemplates in another aspect a method of producing a highly doped region in a microelectronic device structure including a doped material and an active region material, such method c omprising (i) forming an intermediate layer between the doped material and the active region material to produce an interfacial region of increased strain, in relation to a corresponding microelectronic device structure lacking such intermediate layer and wherein the doped material and active region material are contiguous to one another, and (ii) effecting transport of dopant from the doped material toward the active region material so that dopant is accumulated in the interfacial region of increased strain.
• the microelectronic device structure can be of any suitable type, e.g., a ffl-nitride optoelectronic device structure, comprising a ffl-nitride material, and the dopant can include any suitable species, e.g., Si, Mg, Be, Fe, Zn, O, Ge, etc.
• step (ii) of transport of dopant from the doped material toward the active region material is utilized to effect channel definition of the microelectronic device structure.
• step (ii) of transport of dopant from the doped material toward the active region material can in another aspect be carried out for sufficient time to remove dopant from the doped material without removing the charge contribution associated with the dopant.
• the step (ii) of transport of dopant from the doped material toward the active region material, so that dopant is accumulated in the interfacial region of increased strain, can be effected by an elevated temperature condition that is kmetically favorable for such transport of the dopant.
• a further aspect of the invention contemplates a method of engineering tunneling probability of carriers in an impurity diffusion barrier layer of a ffl-nitride device including doped and active regions having such impurity diffusion barrier layer therebetween.
• the invention contemplates a multiple quantum well UV LED structure including a Mg-doped p-AlGaN layer, an active region, and a magnesium diffusion barrier layer therebetween, wherein the magnesium diffusion barrier layer comprises AIN.
• the approach of the present invention while described hereinabove in connection with the use of p-type layers, can also be utilized in n-layers.
• the barrier approach of the present invention is usefully employed in a wide variety of microelectronic devices, including, without limitation, blue light-emitting diodes (LEDs), green LEDs, blue laser diodes (LDs), UV LEDs, UV LDs, heterojunction bipolar transistors (HBTs), etc.
• LEDs blue light-emitting diodes
• LDs blue laser diodes
• UV LEDs UV LDs
• HBTs heterojunction bipolar transistors
• the thickness of the high-Al content Al x Ga y N layer can be widely varied in the broad practice of the present invention, as is readily determinable by those skilled in the art without undue experimentation. In specific applications, thicknesses in a range of from about 5 to about 200 Angstroms in thickness can be advantageously employed to suppress migration/diffusion of dopant species. In other applications, the thickness of the barrier layer is desirably in a range of from about 10 Angstroms to 100 Angstroms, more preferably from about 10 to about 75 Angstroms, and most preferably from about 10 to about 60 Angstroms.
• the value of x can be at least 0.60, 0.75, 0.80, 0.90 or 0.95.
• the minimum aluminum concentration required depends in part on the device processing requirements and in particular, the thermal budget for the device (time and temperature).
• the specific composition and amount of aluminum necessary in the barrier layer for effective migrative and diffusional resistance in a given application of the invention is readily determinable within the skill of the art, based on the disclosure herein.
• illustrative process conditions that are usefully employed for barrier layer growth in accordance with the invention include temperature in a range of from about 900 to about 1500°C, pressure in a range of from about 1 to about 1000 torr, V/HI ratio in a range of from about 1 to about 100,000 and growth rates of about O.Olum/hr to lOum/hr.
• T 1220°C
• P 100mbar
• Vffl 2500 and growth rate of 0.18um/hr
• the high-Al AlGaN barrier layer technology of the invention is usefully employed to fabricate ffl-nitride electronic device structures in which migration and/or diffusion of unwanted material, e.g., dopant species, into active regions of the ffl-nitride device stmcture is substantially reduced or even eliminated by the provision of such barrier layer.
• barrier layer structure enables the fabrication of highly efficient electronic devices, such as optoelectronic devices having substantially improved device lifetimes, higher luminous efficiency and lower heat production and operation, relative to corresponding optoelectronic devices lacking the barrier layer structure of the invention.
• the barrier layer structures of the invention may be utilized to engineer the tunneling probability of carriers in the impurity diffusion barrier layer, in devices such as multiple quantum well (MQW) ultraviolet light emitting diode devices.
• the barrier layer of the invention may also be employed in specific device applicatons to localize dopants in interfacial regions where a high degree of strain or other material differences may be present, to yield highly doped regions for contact formation.
• the barrier layer structure of the invention alternatively may be employed to effect channel definition, in order to optimize the performance of the device including such barrier layer.

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• 2004
  • 2004-05-06 WO PCT/US2004/014171 patent/WO2004102153A2/en not_active Ceased
  • 2004-05-06 US US10/840,515 patent/US7282744B2/en not_active Expired - Lifetime
  • 2004-05-06 JP JP2006532828A patent/JP2007504682A/ja active Pending
  • 2004-05-07 TW TW093112874A patent/TWI244223B/zh not_active IP Right Cessation

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