Showing papers on "Gallium nitride published in 1996"
TL;DR: The elastic constants of GaN have been determined using Brillouin scattering; in GPa they are: C11=390, C33=398, C44=105, C66=123, C12=145, and C13=106.
Abstract: The elastic constants of GaN have been determined using Brillouin scattering; in GPa they are: C11=390, C33=398, C44=105, C66=123, C12=145, and C13=106. Our values differ substantially from those quoted in the literature which were obtained from the determination of mean square displacement of atoms measured by x‐ray diffraction.
554 citations
TL;DR: In this paper, the authors review recent progress in the group-III nitride and related materials, and electronic and optical devices based on them, focusing on the current status of wide bandgap gallium nitride, and related semiconductors from both the materials and devices points of view.
460 citations
Patent•
15 Apr 1996TL;DR: In this paper, a double heterostructure for a light emitting diode consisting of a layer of aluminum gallium nitride having the first conductivity type, a layer with the opposite conductivities, and an active layer of gallium-nitride between the two layers is presented.
Abstract: A double heterostructure for a light emitting diode comprises a layer of aluminum gallium nitride having a first conductivity type; a layer of aluminum gallium nitride having the opposite conductivity type; and an active layer of gallium nitride between the aluminum gallium nitride layers, in which the gallium nitride layer is co-doped with both a Group II acceptor and a Group IV donor, with one of the dopants being present in an amount sufficient to give the gallium nitride layer a net conductivity type, so that the active layer forms a p-n junction with the adjacent layer of aluminum gallium nitride having the opposite conductivity type.
429 citations
TL;DR: A thermal reaction of Li3N and GaCl3 in which benzene was used as the solvent under pressure has been carried out for the preparation of 30-nanometer particles of gallium nitride (GaN) at 280°C, and the yield of GaN reached 80%.
Abstract: A thermal reaction of Li3N and GaCl3 in which benzene was used as the solvent under pressure has been carried out for the preparation of 30-nanometer particles of gallium nitride (GaN) at 280°C. This temperature is much lower than that of traditional methods, and the yield of GaN reached 80%. The x-ray powder diffraction pattern indicated that sample was mainly hexagonal-phase GaN with a small fraction of rocksalt-phase GaN, which has a lattice constant a = 4.100 angstroms. This rocksalt structure, which had been observed previously only under high pressure (at least 37 gigapascals) was observed directly with high-resolution electron microscopy.
398 citations
TL;DR: In this article, the authors measured the lattice parameters of gallium nitride using high-resolution x-ray diffraction and compared the differences between the samples in terms of their concentrations of free electrons and structural defects.
Abstract: Lattice parameters of gallium nitride were measured using high‐resolution x‐ray diffraction. The following samples were examined: (i) single crystals grown at pressure of about 15 kbar, (ii) homoepitaxial layers, (iii) heteroepitaxial layers (wurtzite structure) on silicon carbide, on sapphire, and on gallium arsenide, (iv) cubic gallium nitride layers on gallium arsenide. The differences between the samples are discussed in terms of their concentrations of free electrons and structural defects.
381 citations
TL;DR: In this article, the authors investigated the effect of the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation on the dislocation structure of GaN films.
Abstract: The properties of 1.2 μm thick GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation. The different nitridation schemes of sapphire strongly affect the dislocation structure of GaN films resulting in a decrease of the dislocation density from 2×1010 to 4×108 cm−2 for shorter NH3 preflow times. Room‐ and low‐temperature electron transport characteristics of these films are specifically affected by the dislocation structure. A 300 K electron mobility as high as 592 cm2/V s was obtained for a short ammonia preflow whereas a long nitridation caused the mobility to drop to 149 cm2/V s. Additionally, the photoluminescence quality deteriorates for samples with a long sapphire nitridation time.
280 citations
Patent•
17 Jun 1996
TL;DR: In this paper, a gallium nitride-based III-V Group compound semiconductor device has been proposed, where an ohmic electrode is formed of a metallic material, and has been annealed.
Abstract: A gallium nitride-based III-V Group compound semiconductor device has a gallium nitride-based III-V Group compound semiconductor layer provided over a substrate, and an ohmic electrode provided in contact with the semiconductor layer. The ohmic electrode is formed of a metallic material, and has been annealed.
251 citations
TL;DR: In this article, a theory for the electronic band structure and the free-carrier optical gain of wurtzite-strained quantum-well lasers is presented, taking into account the strain-induced band-edge shifts and the realistic band structures of the GaN-AlGaN wurtZite crystals.
Abstract: A theory for the electronic band structure and the free-carrier optical gain of wurtzite-strained quantum-well lasers is presented. We take into account the strain-induced band-edge shifts and the realistic band structures of the GaN wurtzite crystals. The effective-mass Hamiltonian, the basis functions, the valence band structures, the interband momentum matrix elements, and the optical gain are presented with analytical expressions and numerical results for GaN-AlGaN strained quantum-well lasers. This theoretical model provides a foundation for investigating the electronic and optical properties of wurtzite-strained quantum-well lasers.
227 citations
TL;DR: In this paper, temperature dependencies of the electron mobility in the two-dimensional electron gas (2DEG) in AIGaN/GaN heterostructures and in doped bulk GaN were reported.
Abstract: We report on temperature dependencies of the electron mobility in the two-dimensional electron gas (2DEG) in AIGaN/GaN heterostructures and in doped bulk GaN. Calculations and experimental data show that the polar optical scattering and ionized impurity scattering are the two dominant scattering mechanisms in bulk GaN for temperatures between 77 and 500K. In the 2DEG in AIGaN/GaN heterostructures, the piezoelectric scattering also plays an important role. Even for doped GaN, with a significant concentration of ionized impurities, a large volume electron concentration in the 2DEG significantly enhances the electron mobility, and the mobility values close to 1700 cm2/Vs may be obtained in the GaN 2DEG at room temperature. The maximum measured Hall mobility at 80K is nearly 5000 cm2/Vs compared to approximately 1200 cm2/Vs in a bulk GaN layer. With a change in temperature from 300 to 80K, the 2DEG in our samples changes from nondegenerate and weakly degenerate to degenerate. Therefore, in order to interpret the experimental data, we propose a new interpolation formula for low field mobility limited by the ionized impurity scattering. This formula is valid for an arbitrary degree of the electron gas degeneracy. Based on our theory, we show that the mobility enhancement in the 2DEG is related to a much higher volume electron concentration in the 2DEG, and, hence, to a more effective screening.
205 citations
TL;DR: Fasol as discussed by the authors describes the development of this device, which may have major applications in optical data storage and computer displays, and the corporate culture that fostered its creation, and describes how a researcher at a medium-sized company in Japan developed a long-sought device, a laser diode operating at room temperature that emits blue light.
Abstract: In December 1995, a researcher at a medium-sized company in Japan announced the development of a long-sought device—a laser diode operating at room temperature that emits blue light. In his Perspective, Fasol describes the development of this device, which may have major applications in optical data storage and computer displays, and the corporate culture that fostered its creation.
166 citations
Patent•
27 Dec 1996TL;DR: In this paper, a method of growing gallium nitride on a spinel substrate by providing a supporting substrate having a surface, and disposing a plurality of buffer layers on the surface of the supporting substrate was presented.
Abstract: A method of growing gallium nitride on a spinel substrate by providing a supporting substrate having a surface, and disposing a plurality of buffer layers on the surface of the supporting substrate. The plurality of buffer layers including a first buffer layer of aluminum oxynitride having a low percentage of mismatch to the spinel substrate. The second buffer layer is disposed on the first buffer layer and includes a plurality of layers of a graded aluminum oxynitride having a low dislocation density. A third buffer layer of aluminum nitride is disposed on the second buffer layer. A fourth buffer layer of gallium nitride is disposed on the third buffer layer. Subsequently, a photonic device structure, such as a laser, LED or detector, an electronic device structure, such as a field effect transistor or modulation doped field effect transistor, or an optical waveguide is fabricated on the fourth buffer layer.
TL;DR: In this article, the diffusion length of holes in n-type GaN is found to decrease from 3.4 to 1.2 μm in the doping range of 5×1015-2×1018 cm−3.
Abstract: Minority carrier diffusion length in epitaxial GaN layers was measured as a function of majority carrier concentration and temperature. The diffusion length of holes in n‐type GaN is found to decrease from 3.4 to 1.2 μm in the doping range of 5×1015–2×1018 cm−3. The experimental results can be fitted by assuming the Einstein relation and by the experimental dependence of hole mobilities on carrier concentration. The low injection carrier lifetime of ∼15 ns, used in the fit, is largely independent of the doping level. The diffusion length, measured for ∼5×1015 and 2×1018 cm−3 dopant concentrations, shows an increase with increasing temperature, characterized by an activation energy Ea of ∼90 meV, independent of the impurity concentration.
TL;DR: In this paper, the electronic properties of wide energy gap zinc-blende structure GaN, AlN, and their alloys Ga1−xAlxN were investigated using the empirical pseudopotential method.
Abstract: The electronic properties of wide‐energy gap zinc‐blende structure GaN, AlN, and their alloys Ga1−xAlxN are investigated using the empirical pseudopotential method Electron and hole effective mass parameters, hydrostatic and shear deformation potential constants of the valence band at Γ and those of the conduction band at Γ and X are obtained for GaN and AlN, respectively The energies of Γ, X, L conduction valleys of Ga1−xAlxN alloy versus Al fraction x are also calculated The information will be useful for the design of lattice mismatched heterostructure optoelectronic devices based on these materials in the blue light range application
TL;DR: In this paper, a Vickers indentation method was used to determine the hardness and fracture toughness of a single crystal gallium nitride (GaN) under an applied load of 2N.
Abstract: Basic mechanical properties of single crystal gallium nitride are measured A Vickers (diamond) indentation method was used to determine the hardness and fracture toughness under an applied load of 2N The average hardness was measured as 12±2 GPa and the average fracture toughness was measured as 079±010 MPa√m These values are consistent with the properties of brittle ceramic materials and about twice the values for GaAs A methodology for examining fracture problems in GaN is discussed
TL;DR: In this paper, the Schottky barrier height of Pt-GaN diodes was determined to be 1.10 eV, which is close to 1.5 eV.
Abstract: Gallium nitride is a highly promising wide band gap semiconductor with applications in high power electronic and optoelectronic devices. Among the devices considered for high power generation is the ubiquitous field‐effect transistors which require Schottky barriers for modulating the channel mobile charge. It is in this context that we have undertaken an investigation of likely metal‐GaN contacts. Here we report on the electrical conduction and other properties of Pt–GaN Schottky diodes. These Schottky diodes were fabricated using n‐GaN grown by the molecular beam epitaxy method. Both capacitance–voltage and current–voltage measurements have been carried out as a function of temperature to gain insight into the processes involved in current conduction. Based on these measurements, physical mechanisms responsible for electrical conduction at low and high voltages and temperatures have been suggested. Schottky barrier height determined from the current–voltage and capacitance–voltage measurements is close to 1.10 eV.
TL;DR: In this article, photothermal deflection spectroscopy (PDS) is used to study the sub-bandgap absorption of hexagonal gallium nitride (GaN) in the energy range from 0.6 to 3.8 eV.
Patent•
16 Apr 1996
TL;DR: In this article, the authors proposed a method to make processing operation of a light emitting device easy by avoiding shortage of light amount from a surface side of light emitting element directly toward an outside caused by a shadowed electrode pad and by eliminating the need for formation of a high reflectance mirror surface in a reflection bowl, etc.
Abstract: PURPOSE: To make processing operation of a light emitting device easy by avoiding shortage of a light amount from a surface side of a light emitting element directly toward an outside caused by a shadowed electrode pad and by eliminating the need for formation of a high reflectance mirror surface in a reflection bowl, etc., as in a conventional method or by reducing mirror finish degree. CONSTITUTION: In a semiconductor light emitting element 1 which is formed by forming a lamination part 6 constituted of an N-type semiconductor layer 3, a light emitting layer 4 and a P-type semiconductor layer 5 on a sapphire substrate 12 and an electrode pad in each surface exposed part of the N-type semiconductor layer 3 and the P-type semiconductor layer 5, at least an electrode pad formed in the semiconductor layer 5 at a surface side of the P-type and N-type semiconductor layers is constituted of a conductive transparent film 12. Desirably, the semiconductor layer 5 wherein the transparent film 12 is formed is constituted of a gallium nitride compound semiconductor layer with light transmitting property and the transparent film 12 is brought into ohmic contact with the semiconductor layer 5.
TL;DR: In this article, the gallium imide precursor is shown to yield upon pyrolysis a rare cubic/hexagonal variety of gallium nitride, GaN, and some control over the average particle size of GaN in the nanosized region is achieved by application of various pyrotechnic schemes.
Abstract: The efficient preparation of the new polymeric gallium imide {Ga(NH)3/2}n from the reaction between [Ga(NMe2)3]2 and NH3 at ambient temperatures is described. The gallium imide precursor is shown by TEM and XRD studies to yield upon pyrolysis a rare cubic/hexagonal variety of gallium nitride, GaN. Some control over the average particle size of GaN in the nanosized region is achieved by application of various pyrolysis schemes.
TL;DR: In this paper, the ammonothermal method was used to synthesize high purity metallic gallium nitride (GaN) crystals at pressures below 5 kbar and temperatures below 550°C, where the main role in low temperature GaN crystallization was played by chemically active and dense ammonia and dissolved mineralizer.
Abstract: GaN crystals are grown using ammonothermal method at pressures below 5 kbar and temperatures below 550°C. In this method, GaN is synthesised from high purity metallic gallium. The main role in the low temperature GaN crystallization is played by the chemically active and dense ammonia and dissolved mineralizer. Morphology of the obtained crystals as well as solubility experiments prove that gallium nitride is dissolved and crystallised from solution. Physical properties of GaN crystals obtained using ammonothermal method depend on the growth conditions and the type of mineralizer. All GaN samples reveal very intensive photoluminescence, also at room temperature. The spectra of crystals grown with lithium compound mineralizer are shifted towards higher energies in comparison to crystals grown with potassium based mineralizer. At helium temperatures, phosphorescence is also observed. PACS numbers: 81.10.Dn
Patent•
12 Apr 1996TL;DR: Optically flat cleaved facet mirrors are fabricated in GaN epitaxial films grown on sapphire by wafer fusing a GaN film with a sappire substrate to a cubic substrate such as an InP or GaAs substrate as mentioned in this paper.
Abstract: Optically flat cleaved facet mirrors are fabricated in GaN epitaxial films grown on sapphire by wafer fusing a GaN film with a sapphire substrate to a cubic substrate such as an InP or GaAs substrate. The sapphire substrate may then partially or entirely removed by lapping, dry etching, or wet etching away a sacrificial layer disposed in the interface between the sapphire substrate and the GaN layer. Thereafter, the cubic InP or GaN substrate is cleaved to produce the cubic crystal facet parallel to the GaN layer in which active devices are fabricated for use in lasers, photodetectors, light emitting diodes and other optoelectronic devices.
TL;DR: In this article, a gallium nitride (GaN) thin film with a wurtzite structure was grown on fused silica (FS) substrates by pulsed laser ablation of a liquid gallium target in the presence of ammonia gas X-ray diffraction measurement shows a single c-axis orientation for the GaN film grown with a thin (<1000 A) zinc oxide (ZnO) film as an alignment layer.
Abstract: Gallium nitride (GaN) thin films with a wurtzite structure were grown on fused silica (FS) substrates by pulsed laser ablation of a liquid gallium target in the presence of ammonia gas X‐ray diffraction measurement shows a single c‐axis orientation for the GaN film grown with a thin (<1000 A) zinc oxide (ZnO) film as an alignment layer There is a great improvement in the surface morphology as well as optical transmission for the GaN film grown on the ZnO buffered FS substrate The energy band gap obtained from the absorption spectrum is about 345 eV
TL;DR: In this article, angular-resolved Raman-scattering experiments on AlN and GaN both grown in the wurtzite structure were performed and it was shown that the transverse polar modes in AlN showed a pronounced angular dispersion.
Abstract: We performed angular-resolved Raman-scattering experiments on AlN and GaN both grown in the wurtzite structure. Our measurements reveal that the transverse polar modes in AlN and GaN show a pronounced angular dispersion. We varied the angle between the phonon-propagation direction and the optical axis between 41° and 90° and observed a frequency shift of the A1(TO) mode in the range of 28 cm−1 in AlN and of 15 cm−1 in GaN. The experimental values agree well with our theoretical calculations which were carried out using the DFT-LDA plane-wave pseudopotential method.
TL;DR: In this paper, the pyroelectric effect in wurtzite n-type GaN films deposited over basal plane sapphire substrates was measured and the voltage drop between the contacts while the sample was subjected to the uniform heating or cooling.
Abstract: We report on the measurements of the pyroeffect in wurtzite n‐type GaN films deposited over basal plane sapphire substrates. We measured the voltage drop between the contacts while the sample was subjected to the uniform heating or cooling. The pyroelectric voltage coefficient extracted from our data is comparable to that of the pyroelectric ceramics (∼104 V/m K). Our results show that the pyroelectric effect in GaN is a combination of a fast response to an initial heat flow and a slower response related to a change in the sample temperature.
TL;DR: In this article, a GaN was grown by molecular beam epitaxy using an rf plasma source and the growth under gallium-rich conditions at 730°C was required to produce high quality layers as indicated by photoluminescence, Hall effect, atomic force microscopy and x-ray diffraction measurements.
Abstract: GaN was grown by molecular beam epitaxy using an rf plasma source. Growth under gallium‐rich conditions at 730 °C was required to produce high quality layers as indicated by photoluminescence, Hall effect, atomic force microscopy, and x‐ray diffraction measurements. Atomic hydrogen has a significant effect for Ga‐rich growth, increasing growth rates by as much as a factor of 2.
TL;DR: In this paper, strong excitonic luminescence in wurtzite GaN at 3.309 and 3.365 eV (T = 6 K) was reported.
Abstract: We report on strong excitonic luminescence in wurtzite GaN at 3.309 and 3.365 eV (T=6 K). These lines lie well below the band gap and are found commonly in layers grown by different techniques and on different substrates. From detailed photoluminescence investigations we find small thermal activation energies and a very weak electron–phonon coupling. The photoluminescence behavior under hydrostatic pressure is indicative of strongly localized defects. These findings are similar to observations of excitons localized at extended defects such as dislocations in II–VI compounds.
TL;DR: In this paper, the results of X-ray diffractometric measurements performed on gallium nitride (wurtzite structure, oriented plates) bulk crystals grown using the high-pressure (12-15 kbar)-high-temperature (about 1800 K) method are presented.
TL;DR: In this paper, the authors investigated selective growth of GaN layers on sapphire substrates for low-loss optical waveguide structures of active and passive photonic devices and found that the cross-sectional shape of the GaN waveguides has a rectangular structure with smooth top and side surfaces.
Abstract: Selective growth of GaN layers on sapphire substrates is investigated for low‐loss optical waveguide structures of active and passive photonic devices. When growth conditions, such as nitridation of the substrate surface and growth temperature, are adjusted to achieve high‐density uniform nucleation on the substrate, we found that the cross‐sectional shape of GaN waveguides has a rectangular structure with smooth top and side surfaces. At 77 K, we observed stimulated emission from the cleaved facet of an optically pumped selectively grown GaN waveguide with a width of 6 μm and a cavity length of 800 μm. Line narrowing was also achieved: with the full width at half‐maximum of the emission spectra decreasing from 11 to 2 nm by increasing a pump power density from 0.013 to 0.05 MW/cm2.
TL;DR: In this article, the results of ion implantation of gallium nitride (GaN) using Si and 23Mg species were reported, showing that native defects in the GaN films dominate over implant doping effects.
Abstract: In this letter, we report the results of ion implantation of GaN using "Si and 23Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 30 keV lOI cm-' Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690 "C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties. 0 1996 American Institute of Plr~sics. (SOOO3-695 1(96)052 19-91 d w in ide band-gap n itrides have generated significant terest within th elast fe wyears for both their blue light-emitting and high-temperature properties.' In particular. gallium nitride (GaN) has been most heavily investigated. c Majo rprogress has bee nmad ein the areas of film growth,' p- and n-type doping'- "as well as device fabrication. 5-7 In addition, there have been reports on selective isolation and doping of GaN via implantation using various ion species, such as H, He, and N for isolation, 8 and Mg:P and Si for doping 9 9In this letter, we report the annealing characteristics of Si and Mg implanted molecular beam epitaxy (MBE) grown GaN. GaN thin films grown on basal sapphire substrates (a- Al&) bv an ion-assisted MBE svstem were used as starting material in this study. A GaN bufier layer - 100 A thick was grown at a substrate temperature of 50 0 °C. Epitaxial growth was subsequently performed between 675 and 750 °C. A Kaufmann ion source was use dto supply activated nitrogen. l oAfter growth. the GaY% samples were implanted with a conventional ion implanter, using SiF4 gas and 3N pure Mg as the sources for the '"Si and 24Mo species. respec- c"
TL;DR: In this article, the etch rate of gallium nitride (GaN) was investigated using low pressure SiCl4/Ar ECR discharges and a maximum etching rate of 960 A/min and good surface morphologies were obtained.
Abstract: Electron cyclotron resonance (ECR) plasma etching characteristics of gallium nitride (GaN) are investigated using low pressure (4–10 mTorr) SiCl4/Ar ECR discharges. The purpose of this effort is to examine the dry etching processes of GaN that do not require hydrogen, which is known to cause carrier compensation in GaN. A maximum etching rate of 960 A/min and good surface morphologies are obtained. The etch rate is found to increase near‐linearly with increasing dc bias, and a minimum dc bias of 100 V is required to initiate etching. Enhanced etching rates are obtained as the fraction of active chemical etchant species (SiCl4) in the discharge is increased. We have also found that the material quality significantly affects the etch rate. The latter decreases with x‐ray rocking curve half‐width and increases with defect density.
TL;DR: In this paper, the effects of high temperature annealing on barrier height and the ideality factor of the Schottky contacts were investigated, and it was shown that Pd metal is suitable as the gate metal of GaN-based FETs for temperatures below 300/spl deg/C.
Abstract: High temperature current-voltage characteristics of Pd Schottky contacts on n-type GaN have been investigated up to 500/spl deg/C. The effects of high temperature annealing on barrier height and the ideality factor of the Schottky contacts were investigated. From the trend of barrier height and ideality, Pd metal is suitable as the gate metal of GaN-based FETs for temperatures below 300/spl deg/C.