Showing papers on "Gallium nitride published in 1999"

Nitride Semiconductors and Devices

Abstract: 1. Introduction.- 2. General Properties of Nitrides.- 2.1 Crystal Structure of Nitrides.- 2.2 Gallium Nitride.- 2.2.1 Chemical Properties of GaN.- 2.2.2 Thermal and Mechanical Properties of GaN.- 2.3 Aluminum Nitride.- 2.3.1 Thermal and Chemical Properties of AlN.- 2.3.2 Mechanical Properties of AlN..- 2.3.3 Electrical Properties of AlN.- 2.3.4 Optical Properties of AlN.- 2.4 Indium Nitride.- 2.4.1 Crystal Structure of InN.- 2.4.2 Mechanical and Thermal Properties of InN.- 2.4.3 Electrical Properties of InN.- 2.4.4 Optical Properties of InN.- 2.5 Ternary and Quaternary Alloys.- 2.5.1 AlGaN Alloy.- 2.5.2 InGaN Alloy.- 2.5.3 InAIN Alloy.- 2.6 Substrates for Nitride Epitaxy.- 2A Appendix: Fundamental Data for Nitride Systems.- 3. Electronic Band Structure of Bulk and QW Nitrides.- 3.1 Band-Structure Calculations.- 3.2 Effect of Strain on the Band Structure of GaN.- 3.3 k*p Theory and the Quasi-Cubic Model.- 3.4 Quasi-Cubic Approximation.- 3.5 Confined States.- 3.6 Conduction Band.- 3.7 Valence Band.- 3.8 Exciton Binding Energy in Quantum Wells.- 3.9 Polarization Effects.- 3A Appendix.- 4. Growth of Nitride Semiconductors.- 4.1 Bulk Growth.- 4.2 Substrates Used.- 4.2.1 Conventional Substrates.- 4.2.2 Compliant Substrates.- 4.2.3 Van der Waals Substrates.- 4.3 Substrate Preparation.- 4.4 Substrate Temperature.- 4.5 Epitaxial Relationship to Sapphire.- 4.6 Growth by Hydride Vapor Phase Epitaxy (HVPE).- 4.7 Growth by OMVPE (MOCVD).- 4.7.1 Sources.- 4.7.2 Buffer Layers.- 4.7.3 Lateral Growth.- 4.7.4 Growth on Spinel (MgAl2O4).- 4.8 Molecular Beam Epitaxy.- 4.8.1 MBE Growth Systems.- 4.8.2 Plasma-Enhanced MBE.- 4.8.3 Reactive-Ion MBE.- 4.8.4 Reactive MBE.- 4.8.5 Modeling of the MBE-Like Growth.- 4.9 Growth on 6H-SiC (0001).- 4.10 Growth on ZnO.- 4.11 Growth on GaN.- 4.12 Growth of p-Type GaN.- 4.13 Growth of n-Type InN.- 4.14 Growth of n-Type Ternary and Quaternary Alloys.- 4.15 Growth of p-Type Ternary and Quaternary Alloys.- 4.16 Critical Thickness.- 5. Defects and Doping.- 5.1 Dislocations.- 5.2 Stacking-Fault Defects.- 5.3 Point Defects and Autodoping.- 5.3.1 Vacancies, Antisites and Interstitials.- 5.3.2 Role of Impurities and Hydrogen.- 5.3.3 Optical Signature of Defects in GaN.- 5.4 Intentional Doping.- 5.4.1 n-Type Doping with Silicon, Germanium and Selenium.- 5.4.2 p-Type Doping.- a) Doping with Mg.- 5.4.3 Optical Manifestation of Group-II Dopant-Induced Defects in GaN.- a) Doping with Beryllium.- b) Doping with Mercury.- c) Doping with Carbon.- d) Doping with Zinc.- e) Doping with Calcium.- f) Doping with Rare Earths.- 5.4.4 Ion Implantation and Diffusion.- 5.5 Defect Analysis by Deep-Level Transient Spectroscopy.- 5.6 Summary.- 6. Metal Contacts to GaN.- 6.1 A Primer for Semiconductor-Metal Contacts.- 6.2 Current Flow in Metal-Semiconductor Junctions.- 6.2.1 The Regime Dominated by Thermionic Emission.- 6.2.2 Thermionic Field-Emission Regime.- 6.2.3 Direct Tunneling Regime.- 6.2.4 Leakage Current.- 6.2.5 The Case of a Forward-Biased p-n Junction.- 6.3 Resistance of an Ohmic Contact.- 6.3.1 Specific Contact Resistivity.- 6.3.2 Semiconductor Resistance.- 6.4 Determination of the Contact Resistivity.- 6.5 Ohmic Contacts to GaN.- 6.5.1 Non-Alloyed Ohmic Contacts.- 6.5.2 Alloyed Ohmic Contacts.- 6.5.3 Multi-Layer Ohmic Contacts.- 6.6 Structural Analysis.- 6.7 Observations.- 7. Determination of Impurity and Carrier Concentrations.- 7.1 Impurity Binding Energy.- 7.2 Conductivity Type: Hot Probe and Hall Measurements.- 7.3 Density of States and Carrier Concentration.- 7.4 Electron and Hole Concentrations.- 7.5 Temperature Dependence of the Hole Concentration.- 7.6 Temperature Dependence of the Electron Concentration.- 7.7 Multiple Occupancy of the Valence Bands.- 7A Appendix: Fermi Integral.- 8. Carrier Transport.- 8.1 Ionized Impurity Scattering.- 8.2 Polar-Optical Phonon Scattering.- 8.3 Piezoelectric Scattering.- 8.4 Acoustic Phonon Scattering.- 8.5 Alloy Scattering.- 8.6 The Hall Factor.- 8.7 Other Methods Used for Calculating the Mobility in n-GaN.- 8.8 Measured vis. a vis. Calculated Mobilities in GaN.- 8.9 Transport in 2D n-Type GaN.- 8.10 Transport in p-Type GaN and AlGaN.- 8.11 Carrier Transport in InN.- 8.12 Carrier Transport in AlN.- 8.12.1 Transport in Unintensionally-Doped and High-Resistivity GaN.- 8.13 Observation.- 9. The p-n Junction.- 9.1 Heterojunctions.- 9.2 Band Discontinuities.- 9.2.1 GaN/AIN Heterostructures.- 9.2.2 GaN/InN and AIN/InN.- 9.3 Electrostatic Characteristics of p-n Heterojunctions.- 9.4 Current-Voltage Characteristics on p-n Junctions.- 9.4.1 Generation-Recombination Current.- 9.4.2 Surf ace Effects.- 9.4.3 Diode Current Under Reverse Bias.- 9.4.4 Effect of the Electric Field on the Generation Current.- 9.4.5 Diffusion Current.- 9.4.6 Diode Current Under Forward Bias.- 9.5 Calculation and Experimental I-V Characteristics of GaN Based p-n Juctions.- 9.6 Concluding Remarks.- 10. Optical Processes in Nitride Semiconductors.- 10.1 Absorption and Emission.- 10.2 Band-to-Band Transitions.- 10.2.1 Excitonuc Transitions.- 10.3 Optical Transitions in GaN.- 10.3.1 Excitonic Transitions in GaN.- a) Free Excitons.- b) Bound Excitons.- c) Exciton Recombination Dynamics.- d) High Injection Levels.- 10.3.2 Free-to-Bound Transitions.- 10.3.3 Donor-Acceptor Transitions.- 10.3.4 Defect-Related Transitions.- a) Yellow Luminescence.- b) Group-II Element Related Transitions.- 10.4 Optical Properties of Nitride Heterostructures.- 10.4.1 GaN/AlGaN Heterostructures.- 10.4.2 InGaN/GaN and InGaN/InGaN Heterostructures.- 11. Light-Emitting Diodes.- 11.1 Current-Conduction Mechanism in LED-Like Structures.- 11.2 Optical Output Power.- 11.3 Losses and Efficiency.- 11.4 Visible-Light Emitting Diodes.- 11.5 Nitride LED Performance.- 11.6 On the Nature of Light Emission in Nitride-Based LEDs.- 11.6.1 Pressure Dependence of Spectra.- 11.6.2 Current and Temperature Dependence of Spectra.- 11.6.3 I-V Characteristics of Nitride LEDs.- 11.7 LED Degradation.- 11.8 Luminescence Conversion and White- Light Generation With Nitride LEDs.- 11.9 Organic LEDs.- 12. Semiconductor Lasers.- 12.1 A Primer to the Principles of Lasers.- 12.2 Fundamentals of Semiconductor Lasers.- 12.3 Waveguiding.- 12.3.1 Analytical Solution to the Waveguide Problem.- 12.3.2 Numerical Solution of the Waveguide Problem.- 12.3.3 Far-Field Pattern.- 12.4 Loss and Threshold.- 12.5 Optical Gain.- 12.5.1 Gain in Bulk Layers.- 12.5.2 Gain in Quantum Wells.- 12.6 Coulombic Effects.- 12.7 Gain Calculations for GaN.- 12.7.1 Optical Gain in Bulk GaN.- 12.7.2 Gain in GaN Quantum Wells.- 12.7.3 Gain Calculations in Wz GaN QW Without Strain.- 12.7.4 Gain Calculations in WZ QW With Strain.- 12.7.5 Gain in ZB QW Structures Without Strain.- 12.7.6 Gain in ZB QW Structures with Strain.- a) Pathways Through Excitons and Localized States.- 12.7.7 Measurement of Gain in Nitrides.- a) Gain Measurement via Optical Pumping.- b) Gain Measurement via Electrical Injection (Pump) and an Optical Probe.- 12.8 Threshold Current.- 12.9 Analysis of Injection Lasers with Simplifying Assumptions.- 12.10 Recombination Lifetime.- 12.11 Quantum Efficiency.- 12.12 Gain Spectra of InGaN Injection Lasers.- 12.13 Observations.- 12.14 A Succinct Review of the Laser Evolution in Nitrides.- References.

High-power microwave GaN/AlGaN HEMTs on semi-insulating silicon carbide substrates

Abstract: Record performance of high-power GaN/Al/sub 0.14/-Ga/sub 0.86/N high-electron mobility transistors (HEMTs) fabricated on semi-insulating (SI) 4H-SiC substrates is reported. Devices of 0.125-0.25 mm gate periphery show high CW power densities between 5.3 and 6.9 W/mm, with a typical power-added efficiency (PAE) of 35.4% and an associated gain of 9.2 dB at 10 GHz. High-electron mobility transistors with 1.5-mm gate widths (12/spl times/125 /spl mu/m), measured on-wafer, exhibit a total output power of 3.9 W CW (2.6 W/mm) at 10 GHz with a PAE of 29% and an associated gain of 10 dB at the -2 dB compression point. A 3-mm HEMT, packaged with a hybrid matching circuit, demonstrated 9.1 W CW at 7.4 GHz with a PAE of 29.6% and a gain of 7.1 dB. These data represent the highest power density, total power, and associated gain demonstrated for a III-nitride HEMT under RF drive.

Nitride based transistors on semi-insulating silicon carbide substrates

Abstract: A high electron mobility transistor (HEMT) is disclosed that includes a semi-insulating silicon carbide substrate, an aluminum nitride buffer layer on the substrate, an insulating gallium nitride layer on the buffer layer, an active structure of aluminum gallium nitride on the gallium nitride layer, a passivation layer on the aluminum gallium nitride active structure, and respective source, drain and gate contacts to the aluminum gallium nitride active structure.

Blue vertical cavity surface emitting laser

Abstract: An independently addressable, vertical cavity surface emitting laser ("VCSEL") emitting light in the blue wavelength range of 390 to 430 nanometers comprises a gallium nitride-based laser structure grown by selective area epitaxy and lateral mask overgrowth By appropriate patterning of a dielectric mask on the gallium nitride layer (204) on a sapphire substrate (202), areas in a second gallium nitride layer (210) can have a low defect density upon which the remainder of the laser structure (218-230) can be formed

Indium tin oxide contacts to gallium nitride optoelectronic devices

Abstract: We have fabricated GaN-based light-emitting diodes using transparent indium tin oxide (ITO) p contacts. ITO-contacted devices required an additional 2 V to drive 10 mA, as compared to similar devices with metal contacts. However, ITO has lower optical absorption at 420 nm (α=664 cm−1) than commonly used thin metal films (α=3×105 cm−1). Uniform luminescence was observed in ITO-contacted devices, indicating effective hole injection and current spreading.

Large-scale synthesis of single crystalline gallium nitride nanowires

Abstract: Large-scale synthesis of single crystalline GaN nanowires in anodic alumina membrane was achieved through a gas reaction of Ga2O vapor with a constant flowing ammonia atmosphere at 1273 K X-ray diffraction, Raman backscattering spectroscopy, scanning electron microscopy, and transmission electron microscopy indicated that those GaN nanowires with hexagonal wurtzite structure were about 14 nm in diameter and up to several hundreds of micrometers in length The growth mechanism of the single crystalline GaN nanowires is discussed

Heteroepitaxial electrodeposition of zinc oxide films on gallium nitride

Abstract: Epitaxial zinc oxide films have been prepared on gallium nitride (0002) substrates by cathodic electrodeposition in an aqueous solution containing a zinc salt and dissolved oxygen at 85 °C. The films have the hexagonal structure with the c axis parallel to that of GaN and the [100] direction in ZnO parallel to the [100] direction in GaN in the (0002) basal plane. The structural quality is attested by the values of the full width at half maximum in θ/2θ x-ray diffraction (XRD) diagrams [0.07° for the (0002) peak] and in five circles XRD diagrams [0.74° for the ZnO (1011) planes compared to 0.47° for the GaN (1011) planes]. The morphology of the layers has been studied by scanning electron microscopy. Before coalescence, arrays of epitaxial single crystalline hexagonal columns are observed with a low dispersion in size, indicating instantaneous tridimensional nucleation. Preliminary results on luminescence properties of the films before and after annealing are presented.

Room temperature lasing at blue wavelengths in gallium nitride microcavities

Abstract: Lasing action has been demonstrated at blue wavelengths in vertical cavity surface-emitting lasers at room temperature. The microcavity was formed by sandwiching indium gallium nitride multiple quantum wells between nitride-based and oxide-based quarter-wave reflectors. Lasing action was observed at a wavelength of 399 nanometers under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nanometer below threshold to less than 0.1 nanometer (resolution limit) above threshold. The result suggests that practical blue vertical cavity surface-emitting lasers can be realized in gallium-nitride-based material systems.

Stress evolution during metalorganic chemical vapor deposition of GaN

Abstract: The evolution of stress in gallium nitride films on sapphire has been measured in real time during metalorganic chemical vapor deposition. In spite of the 16% compressive lattice mismatch of GaN to sapphire, we find that GaN consistently grows in tension at 1050 °C. Furthermore, in situ stress monitoring indicates that there is no measurable relaxation of the tensile growth stress during annealing or thermal cycling.

Extensional piezoelectric coefficients of gallium nitride and aluminum nitride

Abstract: Measurements of piezoelectric coefficients d33 and d31 in wurtzite GaN and AlN using an interferometric technique are presented. We report on the clamped values, d33c of these coefficients found in GaN and AlN thin films, and we derive the respective bulk values, d33b. The clamped value of d33c in GaN single crystal films is 2.8±0.1 pm V−1 which is 30% higher than in polycrystalline films grown by laser assisted chemical vapor deposition. The value of d33b in bulk single crystal GaN is found to be 3.7±0.1 pm V−1. The value of d33c in plasma assisted and laser assisted chemical vapor deposited AlN films was 3.2±0.3 and 4.0±0.1 pm V−1, respectively. The bulk value estimate of d33b in AlN of 5.6±0.2 pm V−1 was deduced. The values of d31, both clamped and bulk, were calculated for wurtzite GaN and AlN. We have also calculated the values of d14 in cubic phase film and bulk GaN and AlN. Interferometric measurements of the inverse piezoelectric effect provide a simple method of identifying the positive direction...

Methods of fabricating gallium nitride microelectronic layers on silicon layers and gallium nitride microelectronic structures formed thereby

Abstract: A gallium nitride microelectronic layer is fabricated by converting a surface of a (111) silicon layer to 3C-silicon carbide. A layer of 3C-silicon carbide is then epitaxially grown on the converted surface of the (111) silicon layer. A layer of 2H-gallium nitride then is grown on the epitaxially grown layer of 3C-silicon carbide. The layer of 2H-gallium nitride then is laterally grown to produce the gallium nitride microelectronic layer. In one embodiment, the silicon layer is a (111) silicon substrate, the surface of which is converted to 3C-silicon carbide. In another embodiment, the (111) silicon layer is part of a Separation by IMplanted OXygen (SIMOX) silicon substrate which includes a layer of implanted oxygen that defines the (111) layer on the (111) silicon substrate. In yet another embodiment, the (111) silicon layer is a portion of a Silicon-On-Insulator (SOI) substrate in which a (111) silicon layer is bonded to a substrate. Lateral growth of the layer of 2H-gallium nitride may be performed by Epitaxial Lateral Overgrowth (ELO) wherein a mask is formed on the layer of 2H-gallium nitride, the mask including at least one opening that exposes the layer of 2H-gallium nitride. The layer of 2H-gallium nitride then is laterally grown through the at least one opening and onto the mask. A second, offset mask also may be formed on the laterally grown layer of 2H-gallium nitride and a second laterally grown layer of 2H-gallium nitride may be overgrown onto the offset mask. Lateral growth of the layer of 2H-gallium nitride also may be performed using pendeoepitaxial techniques wherein at least one trench and/or post is formed in a layer of 2H-gallium nitride to define at least one sidewall therein. The layer of 2H-gallium nitride is then laterally grown from the at least one sidewall. Pendeoepitaxial lateral growth preferably continues until the laterally grown sidewalls coalesce on the top of the posts or trenches. The top of the posts and/or the trench floors may be masked to promote lateral growth and reduce nucleation and vertical growth.

Pendeoepitaxy of gallium nitride thin films

Abstract: Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H–SiC(0001) substrates and produced by organometallic vapor phase epitaxy. Selective lateral growth is forced to initiate from the (1120) GaN sidewalls of etched GaN seed forms by incorporating a silicon nitride seed mask and employing the SiC substrate as a pseudomask. Coalescence over and between the seed forms was achieved. Transmission electron microscopy revealed that all vertically threading defects stemming from the GaN/AlN and AlN/SiC interfaces are contained within the seed forms and a substantial reduction in the dislocation density of the laterally grown GaN. Atomic force microscopy analysis of the (1120) face of discrete pendeoepitaxial structures revealed a root mean square roughness of 0.98 A. The pendeoepitaxial layer photoluminescence band edge emission peak was observed to be 3.454 eV and is blueshifted by 12 meV as compared to the GaN seed layer.

Pendeo-epitaxy: a new approach for lateral growth of gallium nitride films

Abstract: Lateral growth of gallium nitride (GaN) films having a low density of dislocations and suspended from side walls of [0001] oriented GaN columns and over adjacent etched wells has been achieved without the use of, or contact with, a supporting mask or substrate. Pendeo-epitaxy is proposed as the descriptive term for this growth technique. Selective growth was achieved using process parameters that promote lateral growth of the \(\{ 11\bar 20\} \) planes of GaN and disallow nucleation of this phase on the exposed silicon carbide substrate. The large horizontal/vertical growth rate ratio indicate that the diffusion distances and the rates of diffusion of the reactant species along the (0001) surfaces were sufficient to allow them to reach and move along the \(\{ 11\bar 20\} \) surfaces before they were chemically adsorbed. A four-to-five order decrease in the dislocation density was observed via transmission electron microscopy in the free-standing laterally grown GaN relative to that in the GaN columns. Curvature of the \(\{ 11\bar 20\} \) planes as they approached coalescence, and elongated voids below the regions of coalescence were formed. The use of optimized growth conditions or more closely spaced columns should eliminate these voids.

Properties, processing and applications of gallium nitride and related semiconductors

Abstract: This volume contains over 100 articles exploring the latest insights and numeric data on gallium nitride. Papers include information on processing and the exploitation of GaN - together with the related semiconductors AlN, InN and ternary semiconductors - in LEDs, lasers and transistors.

Vertical Geometry InGaN LED

Abstract: A vertical geometry light emitting diode is disclosed that is capable of emitting light in the red, green, blue, violet and ultraviolet portions of the electromagnetic spectrum. The light emitting diode includes a conductive silicon carbide substrate, an InGaN quantum well, a conductive buffer layer between the substrate and the quantum well, a respective undoped gallium nitride layer on each surface of the quantum well, and ohmic contacts in a vertical geometry orientation.

Charge accumulation at a threading edge dislocation in gallium nitride

Abstract: We have performed Monte Carlo calculations to determine the charge accumulation on threading edge dislocations in GaN as a function of the dislocation density and background dopant density. Four possible core structures have been examined, each of which produces defect levels in the gap and may therefore act as electron or hole traps. Our results indicate that charge accumulation, and the resulting electrostatic interactions, can change the relative stabilities of the different core structures. Structures having Ga and N vacancies at the dislocation core are predicted to be stable under nitrogen-rich and gallium-rich growth conditions, respectively. Due to dopant depletion at high dislocation density and the multitude of charge states, the line charge exhibits complex crossover behavior as the dopant and dislocation densities vary.

Ammonothermal Synthesis of Cubic Gallium Nitride

Abstract: Cubic gallium nitride (zinc blende type) was formed by reactions of Ga, gallium iodides, and gallium imide−iodides in supercritical ammonia under acidic conditions above 250 °C. Solvothermal transport and recrystallization of c-GaN occurred above 440 °C.

Gallium nitride-type semiconductor device

Abstract: GaN-type LED or LD made on a (0001)GaN single crystal substrate having natural cleavage planes on sides. A GaN/GaN LED has a shape of a equilateral triangle, parallelogram, trapezoid, equilateral hexagon or rhombus. A GaN/GaN LD has a shape of a parallelogram with cleavage planes on two ends and two sides. Another GaN/GaN LD has a shape of a square with cleavage planes on two ends.

Pendeoepitaxial methods of fabricating gallium nitride semiconductor layers on sapphire substrates

Abstract: More specifically, gallium nitride semiconductor layers may be fabricated by etching an underlying gallium nitride layer on a sapphire substrate, to define at least one post in the underlying gallium nitride layer and at least one trench in the underlying gallium nitride layer. The at least one post includes a gallium nitride top and a gallium nitride sidewall. The at least one trench includes a trench floor. The gallium nitride sidewalls are laterally grown into the at least one trench, to thereby form a gallium nitride semiconductor layer. However, prior to performing the laterally growing step, the sapphire substrate and/or the underlying gallium nitride layer is treated to prevent growth of gallium nitride from the trench floor from interfering with the lateral growth of the gallium nitride sidewalls of the at least one post into the at least one trench. Embodiments of gallium nitride semiconductor structures according to the present invention can include a sapphire substrate and an underlying gallium nitride layer on the sapphire substrate. The underlying gallium nitride layer includes therein at least one post and at least one trench. The at least one post each includes a gallium nitride top and a gallium nitride sidewall. The at least one trench includes a sapphire floor. A lateral gallium nitride layer extends laterally from the gallium nitride sidewall of the at least one post into the at least one trench. In a preferred embodiment, the at least one trench extends into the sapphire substrate such that the at least one post each includes a gallium nitride top, a gallium nitride sidewall and a sapphire sidewall and the at least one trench includes a sapphire floor. The sapphire floor preferably is free of a vertical gallium nitride layer thereon and the sapphire sidewall height to sapphire floor width ratio preferably exceeds about 1/4. A mask may be included on the sapphire floor and an aluminum nitride buffer layer also may be included between the sapphire substrate and the underlying gallium nitride layer. A mask also may be included on the gallium nitride top. The mask on the floor and the mask on the top preferably comprise same material.

Methods of fabricating gallium nitride semiconductor layers by lateral growth from sidewalls into trenches, and gallium nitride semiconductor structures fabricated thereby

Abstract: A sidewall of an underlying gallium nitride layer is laterally grown into a trench in the underlying gallium nitride layer, to thereby form a lateral gallium nitride semiconductor layer. Microelectronic devices may then be formed in the lateral gallium nitride layer. Dislocation defects do not significantly propagate laterally from the sidewall into the trench in the underlying gallium nitride layer, so that the lateral gallium nitride semiconductor layer is relatively defect free. Moreover, the sidewall growth may be accomplished without the need to mask portions of the underlying gallium nitride layer during growth of the lateral gallium nitride layer. The defect density of the lateral gallium nitride semiconductor layer may be further decreased by growing a second gallium nitride semiconductor layer from the lateral gallium nitride layer. In one embodiment, the lateral gallium nitride layer is masked with a mask that includes an array of openings therein. The lateral gallium nitride layer is then grown through the array of openings and onto the mask, to thereby form an overgrown gallium nitride semiconductor layer. In another embodiment, the lateral gallium nitride layer is grown vertically. A plurality of second sidewalls are formed in the vertically grown gallium nitride layer to define a plurality of second trenches. The plurality of second sidewalls of the vertically grown gallium nitride layer are then laterally grown into the plurality of second trenches, to thereby form a second lateral gallium nitride layer. Microelectronic devices are then formed in the gallium nitride semiconductor layer.

Cathodoluminescence mapping of epitaxial lateral overgrowth in gallium nitride

Abstract: The dislocation arrangements in gallium nitride (GaN) films prepared by lateral epitaxial overgrowth (LEO) have been studied by cathodoluminescence mapping and transmission electron microscopy. A very low density of electrically active defects (<10−6 cm−2) in the laterally overgrown material is observed. Individual electrically active defects have been observed that propagate laterally from the line of stripe coalescence into the overgrown material. Additionally, by mapping wavelength-resolved luminescence in an InGaN quantum well grown on top of the overgrown material, these defects are shown to be limited to the underlying material and do not propagate normal to the surface, as in other GaN films. In the seed region, threading dislocation image widths are seen to be nearly identical in the quantum well and the underlying GaN, indicating a comparable upper limit (∼200 nm) for minority carrier diffusion length in InGaN and GaN. Additionally, it is shown that, through processing variation, these lateral defects can be avoided in LEO films and that wavelength-resolved cathodoluminescence is an excellent large-area method for rapidly and quantitatively observing variations in process development.

Semiconductor device and method of manufacturing the same

Abstract: There is disclosed a semiconductor device formed on a sapphire substrate, for example, a blue LED of a double-hetero structure having a laminated structure which comprises a first cladding layer made of a first conductivity type gallium nitride based semiconductor, an active layer made of a gallium nitride based semiconductor into which impurity is not doped intentionally, and a second cladding layer made of a second conductivity type gallium nitride based semiconductor which being opposite to the first conductivity type on a sapphire substrate. A surface of the sapphire substrate is polished to have optical transmissivity of more than 60%.

CRYSTAL GROWING METHOD FOR SINGLE-CRYSTAL GaN, AND SINGLE-CRYSTAL GaN SUBSTRATE AND MANUFACTURING METHOD THEREOF

Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing GaN single-crystal with low dislocation which is 106 cm-2 or less SOLUTION: In the crystal growing method of single-crystal gallium nitride, the growth surface of gaseous phase growth is provided with not a plane state but a three-dimensional facet structure, and crystal growth is realized while the facet structure is not embedded but maintained as it is so that dislocation can be reduced

Integration of GaN thin films with dissimilar substrate materials by Pd-In metal bonding and laser lift-off

Abstract: Gallium nitride (GaN) thin films grown on sapphire substrates were successfully bonded and transferred onto GaAs, Si, and polymer “receptor” substrates using a low-temperature Pd-In bond followed by a laser lift-off (LLO) process to remove the sapphire growth substrate. The GaN/sapphire structures were joined to the receptor substrate by pressure bonding a Pd-In bilayer coated GaN surface onto a Pd coated receptor substrate at a temperature of 200°C. X-ray diffraction showed that the intermetallic compound PdIn3 had formed during the bonding process. LLO, using a single 600 mJ/cm2, 38 ns KrF (248 nm) excimer laser pulse directed through the transparent sapphire substrate, followed by a low-temperature heat treatment, completed the transfer of the GaN onto the “receptor” substrate. Cross-sectional scanning electron microscopy and x-ray rocking curves showed that the film quality did not degrade significantly during the bonding and LLO process.

Brillouin scattering study of bulk gan

Abstract: High-resolution Brillouin scattering experiments have been performed for a high-quality free-standing gallium nitride (GaN) substrate. Elastic stiffness constants are reported. A comparison is made with the results of an earlier study for a GaN thin film on sapphire substrate.

Effect of surface treatment by KOH solution on ohmic contact formation of p-type GaN

Abstract: The lowest contact resistivity was achieved by the surface treatment of p-type GaN using KOH solution prior to Pd/Au metal deposition. For the p-type GaN with a hole concentration of 2.9×1016/cm3, the contact resistivity decreased from 2.9×10−1 to 7.1×10−3 Ω cm2 by the surface treatment. This is the lowest value among the previous results ever reported on the formation of ohmic contacts to p-type GaN. The surface treatment is effective in removing the surface oxides formed on p-type GaN during the epitaxial growth which play a role to inhibit the hole transport from metal to p-type GaN.

Synthesis and Growth of Gallium Nitride by the Chemical Vapor Reaction Process (CVRP)

Abstract: A new process for synthesis and bulk crystal growth of GaN is described. GaN single crystal c-plane platelets up to 9mm by 2mm by 100µm thick have been grown by the Chemical Vapor Reaction Process (CVRP). The reaction between gallium and a nitrogen precursor is produced by sublimation of solid ammonium chloride in a carrier gas, which passes over gallium at a temperature of approximately 900°C at near atmospheric pressures. Growth rates for the platelets were 25-100 µm/hr in the hexagonal plane. Seeded growth in the c-direction was also accomplished by re-growth on previously grown c-plane platelets. The crystals were characterized by X-ray diffractometry, atomic force microscopy, secondary ion mass spectrometry, inert gas fusion, and room temperature Hall effect and resistivity measurements.

Process for preparing bulk cubic gallium nitride

Abstract: Bulk cubic gallium nitride is made by charging into a reaction vessel to a fill of 25-95% having a temperature difference between its ends of at least 1° C. a gallium precursor, sufficient amount of an acid mineralizer to form product zinc blende gallium nitride, and sufficient amount of ammonia to at least solubilize the precursor; sealing the reaction vessel; heating contents of the reaction vessel to at least 150° C. while autogenously pressurizing contents of the reaction vessel to at least 500 psi for a duration sufficient to form the product zinc blend gallium nitride; cooling contents of the reaction vessel; and removing from the reaction vessel the product zinc blende gallium nitride.

Epitaxial growth of gallium nitride thin films on A-Plane sapphire by molecular beam epitaxy

Abstract: In this article, we propose a crystallographic model to describe epitaxy of GaN on (1120) sapphire (A plane). The (1102) cleavage plane in sapphire is shown to extend to the GaN lattice as the (1120) plane, facilitating the formation of cleaved facets. It is shown that, although the lattice mismatch is much smaller than in the case of epitaxy on (0001), the difference in the planar symmetry in this case results in high-strained bonds near the interface. The use of nitridation and a low temperature buffer is therefore necessary. A systematic study of GaN growth on the A-plane sapphire by plasma-assisted molecular beam epitaxy was carried out to study the effects of plasma nitridation of the substrate and the growth of a low temperature GaN buffer on the structure and optoelectronic properties of the films. Transmission electron microscopy (TEM) studies indicate that films grown on substrates which were not nitridated prior to growth have a significant fraction of zinc-blende domains and poor orientation relationship with the substrate. On the contrary, nitridation leads to films with superior structural and optoelectronic properties. The low temperature GaN buffer, grown on nitridated substrates, was found to also have a pronounced effect on the optoelectronic properties of the GaN films, especially in those with low carrier concentrations. The correlation between TEM and photoluminescence studies suggests that the transition at 3.27 eV can be attributed to the cubic domains in the films.