Showing papers on "Gallium nitride published in 1994"

Buffer structure between silicon carbide and gallium nitride and resulting semiconductor devices

Abstract: A transition crystal structure is disclosed for providing a good lattice and thermal match between a layer of single crystal silicon carbide (25) and a layer of single crystal gallium nitride (24). The transition structure comprises a buffer formed of a first layer of gallium nitride and aluminum nitride (22), and a second layer of gallium nitride and aluminum nitride (23) adjacent to the first layer. The mole percentage of aluminum nitride in the second layer (23) is substantially different from the mole percentage of aluminum nitride in the first layer (22). A layer of single crystal gallium nitride (24) is formed upon the second layer of gallium nitride and aluminum nitride. In preferred embodiments, the buffer further comprises an epitaxial layer of aluminum nitride upon a silicon carbide substrate.

Raman scattering from LO phonon‐plasmon coupled modes in gallium nitride

Abstract: Raman spectra of n‐type gallium nitride with different carrier concentrations have been measured. The LO phonon band shifted towards the high‐frequency side and broadened with an increase in carrier concentration. Results showed that the LO phonon was coupled to the overdamped plasmon in gallium nitride. The carrier concentrations and damping constants were determined by line‐shape fitting of the coupled modes and compared to values obtained from Hall measurements. The carrier concentrations obtained from the two methods agree well. As a result, the dominant scattering mechanisms in gallium nitride are deformation‐potential and electro‐optic mechanisms.

Gallium nitride-based III-V group compound semiconductor device and method of producing the same

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.

Thermal expansion of gallium nitride

Abstract: Lattice constants of gallium nitride (wurzite structure) have been measured at temperatures 294–753 K. The measurements were performed by using x‐ray diffractometry. Two kinds of samples were used: (1) bulk monocrystal grown at pressure of 15 kbar, (2) epitaxial layer grown on a sapphire substrate. The latter had a smaller lattice constant in a direction parallel to the interface plane by about 0.03%. This difference was induced by a higher thermal expansion of the sapphire with respect to the GaN layer. However, this thermal strain was created mainly at temperatures below 500–600 K. Above these temperatures the lattice mismatch in parallel direction diminished to zero at a temperature of about 800 K.

Low-strain laser structures with group III nitride active layers

Abstract: A Group III nitride laser structure is disclosed with an active layer that includes at least one layer of a Group III nitride or an alloy of silicon carbide with a Group III nitride, a silicon carbide substrate, and a buffer layer between the active layer and the silicon carbide substrate. The buffer layer is selected from the group consisting of gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having the formula A x B 1-x N, where A and B are Group III elements and where x is zero, one, or a fraction between zero and one, and alloys of silicon carbide with such ternary Group III nitrides. In preferred embodiments, the laser structure includes a strain-minimizing contact layer above the active layer that has a lattice constant substantially the same as the buffer layer.

Current/voltage characteristic collapse in AlGaN/GaN heterostructure insulated gate field effect transistors at high drain bias

Abstract: The authors describe the current/voltage characteristic collapse under a high drain bias in AlGaN/GaN heterostructure insulated gate field effect transistors (HIGFETs) grown on sapphire substrates. These devices exhibit a low resistance state and a high resistance state, before and after the application of a high drain voltage, respectively. At room temperature, the high resistance state persists for several seconds. The device can also be returned into the low resistance state by exposing it to optical radiation. Electron trapping in the gate insulator near the drain edge of the gate is a possible mechanism for this effect, which is similar to what has been observed in AlGaAs/GaAs HFETs at cryogenic temperatures.

p‐type gallium nitride by reactive ion‐beam molecular beam epitaxy with ion implantation, diffusion, or coevaporation of Mg

Abstract: Gallium nitride is one of the most promising materials for ultraviolet and blue light‐emitting diodes and lasers. The principal technical problem that limits device applications has been achieving controllable p‐type doping. Molecular beam epitaxy assisted by a nitrogen ion beam produced p‐type GaN when doped via ion implantation, diffusion, or coevaporation of Mg. Nearly intrinsic p‐type material was also produced without intentional doping, exhibiting hole carrier concentrations of 5×1011 cm−3 and hole mobilities of over 400 cm2/V/s at 250 K. This value for the hole mobility is an order of magnitude greater than previously reported.

Growth of gallium nitride by electron‐cyclotron resonance plasma‐assisted molecular‐beam epitaxy: The role of charged species

Abstract: The role of ionic and nonionic excited species of nitrogen in the growth of GaN thin films by electron‐cyclotron resonance (ECR) plasma‐assisted molecular‐beam epitaxy has been investigated. It was found that the kinetics of film growth is significantly affected by the microwave power in the ECR discharge. Specifically, a transition from the island to a layer‐by‐layer and, finally, to a three‐dimensional growth has been observed as a function of power. These morphological changes are accompanied by degradation of the electrical and luminescence properties, a result attributable to increased native defects and impurities. Secondary‐ion‐mass spectroscopic (SIMS) analysis indicates that impurity levels in the films increase with the plasma power levels used during the growth. To study the relative role of ion‐induced native defects in these films, strategies for charged species extraction were developed by using an off‐axis solenoid to modify the magnetic environment during growth. Films grown under a reduce...

Hydrogenation of p‐type gallium nitride

Abstract: Hole concentrations of up to 1019 cm−3 have been reported for GaN:Mg films grown by molecular beam epitaxy without any post‐growth treatment. Comparing results from Hall measurements and secondary ion mass spectrometry, we observe doping efficiencies of up to 10% at room temperatures in such p‐type material. By hydrogenating at temperatures above 500 °C, the hole concentration can be reduced by an order of magnitude. A new photoluminescence line at 3.35 eV is observed after this treatment, both in p‐type and unintentionally doped n‐type material, which suggests the introduction of a hydrogen‐related donor level in GaN.

Characteristics of chemically assisted ion beam etching of gallium nitride

Abstract: Chemically assisted ion beam etching (CAIBE) characteristics of gallium nitride (GaN) have been investigated using a 500‐eV Ar ion beam directed onto a sample in a Cl2 ambient. Enhanced etch rates were obtained for samples etched in the presence of Cl2 over those etched only by Ar ion milling at a substrate temperature of 20 °C. The CAIBE etch rates were further enhanced at higher substrate temperatures whereas etch rates for Ar ion milling were not influenced by substrate temperature. Etch rates as high as 210 nm/min are reported. The etch rates reported here are the highest so far reported for GaN. Anisotropic etch profiles and smooth etched surfaces in GaN have been achieved with CAIBE.

Crystal growth method of gallium nitride-based compound semiconductor

Abstract: PURPOSE: To obtain a crystal growth method which improves the crystallinity of a gallium nitride-based compound semiconductor to be grown on a buffer layer and in which the gallium nitride-based compound semiconductor is grown stably and at good yield. CONSTITUTION: A reaction gas is supplied into a reaction chamber, and a gallium nitride-based compound semiconductor is grown on a buffer layer by an organometallic compound vapor growth method. Alternatively, both a buffer layer and a gallium nitride-based compound semiconductor are grown by an organometallic compound vapor growth method. Alternatively, before a gallium nitride-based compound semiconductor is grown inside a reaction chamber in which the gallium nitride-based compound semiconductor is grown, a buffer layer whose general expression is Ga x Al 1-x N (where X is within a range of 0.5≤X≤1) is grown at a growth temperature of 200°C or higher and 900°C or lower. COPYRIGHT: (C)1995,JPO

Crystallography of epitaxial growth of wurtzite-type thin films on sapphire substrates

Abstract: In this article, we present a crystallographic model to describe the epitaxial growth of wurtzite‐type thin films such as gallium nitride (GaN) on different orientations of sapphire (Al2O3) substrates. Through this model, we demonstrate the thin films grown on (00⋅1)Al2O3 have a better epilayer‐substrate interface quality than those grown on (01⋅2)Al2O3. We also show the epilayer grown on (00⋅1)Al2O3 are gallium‐terminated, and both (00⋅1) and (01⋅2) surfaces of sapphire crystals are oxygen‐terminated.

Infrared luminescence of residual iron deep level acceptors in gallium nitride (GaN) epitaxial layers

Abstract: A characteristic infrared luminescence band, dominated by a zero‐phonon line at 1.30 eV has been consistently detected in gallium nitride (GaN) epitaxial layers. It is assigned to the intra‐3d‐shell transitions 4T1(G)→6A1(S) of omnipresent iron trace impurities, Fe3+Ga(3d5). Another infrared emission is often also observed at 1.19 eV. This is tentatively assigned to chromium trace impurities, Cr4+Ga(3d2). The role of iron and chromium as minority‐carrier lifetime killers in GaN‐based optoelectronic devices is suggested from these data.

Reactive ion etching of gallium nitride using hydrogen bromide plasmas

Abstract: The characteristics of the reactive ion etching (RIE) of gallium nitride (GaN) have been investigated using HBr, 1:1 HBr:Ar, and 1:1 HBr:H/sub 2/ plasmas. Etch rates were found to increase with plasma self-bias voltage for all gas mixtures exceeding 60 nm/min at -400 V for pure HBr. Higher etch rates were obtained for pure HBr than for HBr mixtures with Ar and H/sub 2/. Chamber pressure was also found to slightly affect etch rates for the pressure ranges investigated. The anisotropy of etched profiles was found to improve with increasing pressure. Smooth etched surfaces are also demonstrated. >

Method of depositing a gallium nitride-based III-V group compound semiconductor crystal layer

Abstract: A method of depositing a gallium nitride-based III-V Group compound semiconductor crystal layer over a substrate by a metalorganic chemical vapor deposition technique. A reaction gas is supplied to a surface of a heated substrate in a direction parallel or oblique to the substrate. The gallium nitride-based III-V Group compound semiconductor crystal layer is grown on the heated substrate, while introducing a pressing gas substantially in a vertical direction toward the substrate to press the reaction gas against the entire surface of the substrate, under atmospheric pressure or a higher pressure.

Manufacture of gallium nitride compound semiconductor chip

Abstract: PROBLEM TO BE SOLVED: To provide a method of cutting a gallium compound semiconductor wafer where a sapphire substrate is used into chips prescribed in size and shape high in efficiency protecting their cut surfaces against cracking and chipping. SOLUTION: This manufacturing method is realized by improving a usual manufacturing method where a gallium nitride compound semiconductor chip is manufactured from a wafer, wherein a first dividing groove 11 is provided in a line to a gallium nitride semiconductor layer so as to reach to a sapphire substrate as deep as prescribed penetrating through the gallium nitride semiconductor layer. Furthermore, a second dividing groove 22 whose width W2 is smaller than that W1 of the first groove 11 is provided to the rear of the sapphire substrate 1 of the wafer corresponding to the first dividing groove 11. The wafer is divided into chips along the first and the second dividing groove. COPYRIGHT: (C)1998,JPO

Method for crystal growth of n-type gallium nitride compound semiconductor

Abstract: PURPOSE: To improve the crystallizability of other nitride semiconductors grown on the surface of an n-type nitride semiconductor layer and to improve the efficiency of a light emitting element and a photoreceptor element by providing a method for growth by reducing the lattice defect of the n-type nitride semiconductor surface. CONSTITUTION: At least one layer of a second n-type nitride semiconductor layer 33 (Ina Alb Ga1-a-b N, 0<=a, 0<=b, a+b<=1) whose composition differs from an n-type nitride semiconductor layer 3' is grown in the n-type nitride semiconductor layer 3' growth or the n-type nitride semiconductor layer 3' is grown at least by the thickness of 5μm.

Semiconductor light emitting element and manufacture thereof

Abstract: PURPOSE: To improve the light emitting efficiency with a low cost by laminating a gallium nitride compound semiconductor layer having at least an n-type layer and a p-type layer on a substrate made of a silicon oxide substrate. CONSTITUTION: The one surface of a silicon oxide plate is mirror polished as a substrate 1, and an n-type GaN film is formed thereon by an MOCVD method. When the film forming temperature is low temperature of about 400-700 deg.C, the GaN is formed in a film in a polycrystalline state to become a low temperature buffer layer 2. Thereafter, when it is epitaxially grown at a high temperature of 900-1200 deg.C, a high temperature buffer layer 3 made of GaN single crystalline layer is formed. Further, an n-type clad layer 4, an active layer 5, a P-type clad layer 6 and a cap layer 7 are grown, and a gallium nitride compound semiconductor is laminated. Thus, since it can be formed on a low-cost silicon oxide substrate, a lower-cost blue semiconductor light emitting element than a sapphire can be obtained.

Homoepitaxial Growth of Cubic GaN by Hydride Vapor Phase Epitaxy on Cubic GaN/GaAs Substrates Prepared with Gas Source Molecular Beam Epitaxy.

Abstract: Thick cubic GaN (c-GaN) layers were homoepitaxially grown on c-GaN/(100)GaAs by hydride vapor phase epitaxy (HVPE). The c-GaN crystals used as substrates in this work were prepared by gas source molecular beam epitaxy (GSMBE). When the growth temperature was too low (?700? C) or too high (?1000? C), hexagonal GaN (h-GaN) was included in the grown layer, but pure c-GaN was obtained at 900? C. The growth rate of c-GaN by HVPE in this work was about 1.6 ? m/h, which was 4?10 times higher than that of GSMBE or metalorganic vapor phase epitaxy (MOVPE), and an about 5 ? m thick c-GaN film was obtained by 3-h growth. The X-ray diffraction (XRD) patterns showed only the (200) and (400) c-GaN peaks but no h-GaN one. The cathodoluminescence (CL) spectra exhibited a strong peak at about 365 nm, which corresponds to the band edge emission. No emission due to deep levels was observed.

Manufacture of gallium nitride based semiconductor laser element

Abstract: PURPOSE: To provide a manufacturing method of a laser element which can realize an optical resonance surface on a semiconductor layer, from a wafer wherein gallium nitride based compound semiconductor is laminated in the structure turning to a laser element, on a sapphire substrate. CONSTITUTION: After gallium nitride based compound semiconductor is laminated in the structure of a laser element, on the surface of the (0001) face of a sapphire substrate, the optical resonance surface of a semiconductor laser element is formed by splitting the sapphire substrate, with one face orientation out of the respective side surfaces. COPYRIGHT: (C)1996,JPO

Semiconductor light emitting element and its manufacture

Abstract: PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element using a gallium nitride-based compound semiconductor formed in an electrode structure, having a good ohmic contact characteristic and a superior wire-bondability. SOLUTION: A laminated semiconductor section 10, which contains an n-type layer 3 and a p-type layer 5 both composed of gallium nitride-based compound semiconductors and forms a light-emitting region is provided on the surface of a substrate 1 and a p-side electrode 8 is formed on the surface of the section 10 with a diffused metal layer 7 in between. In addition, an n-side electrode 9 is formed on the part of the n-type layer 3 exposed by removing part of the laminated semiconductor section 10. The n-side electrode 9 consists of an electrode section 91 for ohmic contact and another electrode section 92 for bonding, and the electrode section 92 is provided to cover the top and side faces of the electrode section 91. COPYRIGHT: (C)1999,JPO

Gallium nitride compound semiconductor element

Abstract: PURPOSE: To improve the ohmic contact of a p-type gallium nitride compound semiconductor with its electrode and to reduce the Vf of a light emitting element and a light receiving element using it by using Mg or its alloy to the side in contact with its p-type layer as the electrode of a p-type gallium nitride compound semiconductor device CONSTITUTION: A mask of a predetermined shape is formed on the surface of the p-type GaN layer 7 of a wafer, the layer 7 is etched by dry etching, and the part of an n-type GaN layer 3 to be formed with an electrode is exposed, Then, Ti is evaporated as an n-type electrode 8 and Al in a predetermined shape on the Ti is deposited on the surface of the layer 3 Further, Mg is evaporated, Ni is deposited on the Mg, and further Au is evaporated on the Mg on the substantially entire surface of the layer 7 as a p-type electrode 99 After the evaporations, the wafer is annealed in an inert gas atmosphere, both the electrodes are alloyed, the electrode 99 is made light-transmissive, annealed, and the wafer is then cut in a predetermined shape as a light emitting chip

Gallium nitride based compound semiconductor light receiving element

Abstract: PURPOSE: To provide a light receiving element with an excellent reliability which has its sensitivity in the wide region ranging from near ultraviolet region to red region. CONSTITUTION: In a light receiving element having a double hetero-structure, as a light receiving layer 5, an In x Ga 1-x N layer (0

Comparison of Hydride Vapor Phase Epitaxy of GaN Layers on Cubic GaN/(100)GaAs and Hexagonal GaN/(111)GaAs Substrates.

Abstract: GaN layers were homoepitaxially grown by hydride vapor phase epitaxy (HVPE) on cubic GaN/(100)GaAs and hexagonal GaN/(111)GaAs substrates, and the growth conditions and crystalline qualities were compared between both cases. HVPE GaN layers were epitaxially grown on hexagonal GaN/(111)GaAs substrates when the substrate temperature was below 700°C, whereas on cubic GaN/(100)GaAs substrates, they were epitaxially grown only at substrate temperatures above 800°C. Two-step growth was necessary for higher-quality hexagonal GaN epilayers to be grown at 900°C. The growth rate of HVPE GaN epilayers on hexagonal GaN/(111)GaAs substrates was about 2.5 times higher than that on cubic GaN/(100)GaAs substrates at the same HVPE growth conditions. Cathodoluminescence spectra were measured for HVPE epilayers grown on both substrates.

An ab initio pseudopotential calculation of ground-state and excited-state properties of gallium nitride

Abstract: In this work, the electronic, ground-state and vibrational properties of both alpha -GaN (i.e. wurtzite structure) and the recently fabricated beta -GaN (i.e. zincblende structure) have been studied using the ab initio pseudopotential method within the local density approximation and a simple quasi-particle scheme. The calculated equilibrium lattice constants, bulk moduli, the pressure derivatives of the bulk moduli, and the Al TO( Gamma ) phonon frequency are in good agreement with available experimental and other recent ab initio theoretical results. The self-energy band gap corrections are found to be highly k-dependent. The calculated fundamental band gap is direct in both cases and for the experimental lattice constant is calculated to be 3.36 eV in beta -GaN and 3.48 eV in alpha -GaN, in excellent agreement with experiment.

Growing method of p-type gallium nitride

Abstract: PURPOSE:To furnish a growing method whereby GaN doped with a P-type dopant can be made to be of a P-type of a low resistance during the growth without necessitating any post-treatment. CONSTITUTION:After a gallium nitride compound semiconductor expressed by a general formula InXAlYGa1-X-YN (where 0 /cm -3X10 /cm is made to grow on the gallium nitride compound semiconductor.

Effect of Aluminum Nitride Buffer Layer Temperature on Gallium Nitride Grown by OMVPE

Abstract: Gallium nitride layers were grown by organometallic vapor phase epitaxy on AlN buffer layers deposited in the range of 450-650°C. The GaN growth conditions were kept constant so that changes in film properties were due only to changes in the buffer layer growth temperature. A monotonie improvement in relative crystallinity as measured by double-crystal X-ray diffraction corresponded with a decrease in buffer layer growth temperature. Improvements in GaN electron transport at 300 and 77 K were also observed with decreasing AlN buffer layer temperature. Photoluminescence spectra for the lowest temperatures studied were dominated by sharp excitonic emission, with some broadening of the exciton linewidth observed as the buffer layer growth temperature was increased. The full width at half maximum of the excitonic emission was 2.7 meV for GaN grown on a 450°C buffer layer. These results indicate that minimizing AlN buffer layer temperature results in improvements in GaN film quality.