Showing papers on "Gallium nitride published in 1993"

Light-emitting gallium nitride-based compound semiconductor device

Abstract: A light-emitting gallium nitride-based compound semiconductor device of a double-heterostructure. The double-heterostructure includes a light-emitting layer formed of a low-resistivity In x Ga 1-x N (0

Metal contacts to gallium nitride

Abstract: We report measurements on the nature of aluminum and gold contacts to GaN. The GaN films were deposited onto the R‐plane of sapphire substrates by molecular beam epitaxy and are autodoped n‐type. Metal contacts were deposited by evaporation and were patterned photolithographically. Current‐voltage characterization shows that the as‐deposited aluminum contacts are ohmic while the as‐deposited gold contacts are rectifying. The gold contacts become ohmic after annealing at 575 °C, a result attributed to gold diffusion. The specific contact resistivity of the ohmic aluminum and gold contacts were found by transfer length measurements to be of device quality (10−7–10−8 Ω m2). The results of these studies suggest a direct correlation between barrier height and work function of the metal, consistent with the strong ionic character of GaN.

Monte Carlo simulation of electron transport in gallium nitride

Abstract: The results of an ensemble Monte Carlo simulation of the electron transport in gallium nitride (GaN) are presented. The calculation shows that intervalley electron transfer plays a dominant role in GaN in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. An analytic expression for the polar optical momentum relaxation time for phonon energies larger than the thermal energy is also derived. This expression applies to many wide‐gap semiconductors, such as GaN and SiC, at room temperature since these semiconductors have large polar optical‐phonon energies (on the order of 100 meV). The calculated mobility agrees well with the results of the Monte Carlo calculation.

First-principles calculation of the structural, electronic, and vibrational properties of gallium nitride and aluminum nitride

Abstract: First-principles pseudopotential calculations have been performed on GaN and AlN in the wurtzite and zinc-blende structures. The mixed-basis approach is employed due to the localized nature of the valence charge density in these materials. In the stress calculation within the mixed-basis set, a correction term is introduced to the stress expression in order to make it consistent with the pressure given by the total-energy calculations. The lattice constants in the wurtzite structure are in good agreement with the experimental data. The band gap appears to be direct except for zinc-blende AlN, which has the conduction-band minimum at the X point. The effective mass of the electron is found to be nearly isotropic for both wurtzite GaN and AlN. The agreement of the optical \ensuremath{\Gamma}-phonon frequencies with the Raman experimental data is excellent for wurtzite GaN and good for wurtzite AlN, except for ${\mathit{A}}_{1}$--transverse-optical (${\mathit{A}}_{1}$-TO) mode. The calculated ${\mathit{A}}_{1}$-TO mode frequency of AlN is 11% smaller than the experimental value. Both GaN and AlN are found to have the wurtzite structure in the ground state.

Reactive ion etching of gallium nitride in silicon tetrachloride plasmasa)

Abstract: The reactive ion etching characteristics of gallium nitride (GaN) in silicon tetrachloride plasmas (SiCl4, 1:1/SiCl4:Ar, and 1:1/SiCl4:SiF4) in the pressure range between 20 and 80 mTorr have been investigated. For the pressure range investigated, etch rates are found to be essentially identical for the different gas mixtures and also invariant with pressure. However for all gas mixtures, etch rates increased monotonically with increasing plasma self‐bias voltage exceeding 50 nm/min at 400 V. This is one of the highest etch rate ever reported for GaN. Smooth and anisotropic etch profiles are demonstrated for structures of submicrometer dimensions. The slight overcut observed in the etch profiles is attributed to the significant role of physical ion bombardment in the etching mechanism. Auger electron spectroscopy show that a wet etch in dilute HF is needed to clear the Si (in the form of SiOx) embedded in the near surface of GaN during etching thereby restoring etched surfaces to their virgin state.

High-pressure structure of gallium nitride: Wurtzite-to-rocksalt phase transition.

Abstract: High-pressure energy-dispersive x-ray-diffraction studies were carried out on the III-V compound gallium nitride to 70 GPa using a synchrotron x-ray source. A pressure-induced first-order phase transition from a wurtzite structure to a rocksalt structure was observed to begin at a pressure of 37 GPa.

Electron transport mechanism in gallium nitride

Abstract: The electron transport mechanism in autodoped gallium nitride films grown by electron cyclotron resonance microwave plasma‐assisted molecular beam epitaxy was investigated by studying the temperature dependence of the Hall coefficient and resistivity on samples with various concentrations of autodoping centers. The Hall coefficients go through a maximum as the temperature is lowered from 300 K and then saturate at lower temperatures. The resistivities in the same temperature range initially increase exponentially and then saturate at lower temperatures. These findings are accounted for if a significant fraction of electron transport, even at room temperature, takes place in the autodoping centers and that conduction through these centers becomes dominant at lower temperatures. The activation energy of these centers was found to be on the order of 20–30 meV. When the concentration of the autodoping centers becomes smaller than that of deep compensating defects, the material becomes semi‐insulating and transport by hopping in the compensating defects becomes dominant.

Method of fabricating a gallium nitride based semiconductor device with an aluminum and nitrogen containing intermediate layer

Abstract: Disclosed are a gallium nitride type semiconductor device that has a single crystal of (Ga 1-x Al x ) 1-y In y N, which suppresses the occurrence of crystal defects and thus has very high crystallization and considerably excellent flatness, and a method of fabricating the same. The gallium nitride type semiconductor device comprises a silicon substrate, an intermediate layer consisting of a compound containing at least aluminum and nitrogen and formed on the silicon substrate, and a crystal layer of (Ga 1-x Al x ) 1-y In y N (0≦x≧1, 0≦y≦1, excluding the case of x=1 and y=0). According to the method of fabricating a gallium nitride base semiconductor device, a silicon single crystal substrate is kept at a temperature of 400° to 1300° C. and is held in the atmosphere where a metaloganic compound containing at least aluminum and a nitrogen-containing compound are present to form a thin intermediate layer containing at least aluminum and nitrogen on a part or the entirety of the surface of the single crystal substrate, and then at least one layer or multiple layers of a single crystal of (Ga 1-x Al x ).sub. 1-y In y N are formed on the intermediate layer.

Gallium nitride compound semiconductor light-emitting element

Abstract: PROBLEM TO BE SOLVED: To raise the performance of a nitride semiconductor light emitting element by putting a light emitting element in double hetero structure which has, between a substrate and an active layer, an n-type gallium nitride compound semiconductor layer having such structure that a second nitride semiconductor layer including one kind among Ina Ga1-a N, Aln Ga1-b N (a and b are specified values), etc, is put between first and third nitride semiconductor layers SOLUTION: Putting a second nitride semiconductor layer different in composition in an n-type nitride semiconductor layer will let the second nitride semiconductor layer (buffer layer) works as a buffer layer, which can lighten a crystal defect It is to be desired that this second buffer layer 33 should be a multilayer film where films of InIGa1-a N (0

Thin films and devices of diamond, silicon carbide and gallium nitride

Abstract: The extreme properties of diamond, SiC and GaN provide combinations of attributes for high-power, -temperature, -frequency and optoelectronic applications. The methods of deposition, the results of chemical, structural, microstructural and electrical characterization and device development are reviewed for thin films of these three materials. Problems and areas of future research are also noted.

Light-emitting device of gallium nitride compound semiconductor

Abstract: Disclosed herein is a light-emitting diode of GaN compound semiconductor which emits a blue light from a plane rather than dots for improved luminous intensity. It has an electrode 80 for the high-carrier density n + -layer 3 and an electrode 70 for the high-impurity density i H -layer 52. These electrodes 70 (80) are made up a first Ni layer 71 (81) (100A thick), a second Ni layer 72 (82) (1000A thick), an Al layer 73 (83) (1500A thick), a Ti layer 74 (84) (1000A thick), and a third Ni layer 75 (85) (2500A thick). The Ni layers of dual structure permit a buffer layer to be formed between them. This buffer layer prevents the Ni layer from peeling. The direct contact of the Ni layer with GaN lowers the drive voltage for light emission and increases the luminous intensity.

Growth of gallium nitride thin films by electron cyclotron resonance microwave plasma‐assisted molecular beam epitaxy

Abstract: We report on optimization studies for the growth of GaN films by the electron cyclotron resonance microwave plasma‐assisted molecular beam epitaxy (ECR‐MBE) method on the R plane of sapphire. The films were grown by the reaction of Ga vapor with ECR‐activated molecular nitrogen and their growth kinetics were found to depend strongly on the distance between the ECR condition and the substrate. Single crystalline films with their α plane (1120) parallel to the R plane of sapphire (1012) were grown with the substrate held at 400–700 °C. All films were found to be n type with carrier concentrations varying between 1017 and 1019 cm−3. Films grown at 600 °C were found to have the smallest amount of strain and the highest electron mobility, suggesting that strain might be one of the sources of compensating defects.

Deposition of highly resistive, undoped, and p‐type, magnesium‐doped gallium nitride films by modified gas source molecular beam epitaxy

Abstract: Undoped, highly resistive (≳102 Ω cm) and Mg‐doped, p‐type (0.3 Ω cm) monocrystalline GaN films with a thickness of (4–5)×103 A have been achieved via modified gas source molecular beam epitaxy on AIN buffer layers without the post‐processing procedures of either electron beam irradiation or annealing necessary in chemical vapor deposition (CVD) derived films. The carrier concentrations and mobilities could not be accurately measured in the undoped films; values to 1018 cm−3 and 10 cm2/V s, respectively, have been achieved in the p‐type films. These results indirectly support the hypothesis of Mg‐H complexes as the cause of the difficulty in achieving highly conducting p‐type materials using CVD techniques.

Comparison of the physical properties of GaN thin films deposited on (0001) and (011̄2) sapphire substrates

Abstract: A direct comparison of the physical properties of GaN thin films is made as a function of the choice of substrate orientations. Gallium nitride single crystals were grown on (0001) and (0112) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (0112) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (0112) sapphire. The results of this study show better physical properties of GaN thin films achieved on (0112) sapphire.

Light emitting element of gallium nitride compound semiconductor

Abstract: PURPOSE:To improve an external quantum efficiency of a light emitting element by forming a transparent film, on a surface of the gallium nitride compound semiconductor, of which the refractive index is between the refractive indexes of the compound semiconductor and a sealing material, and suppressing interference of light by multipath reflection inside the semiconductor. CONSTITUTION:A semiconductor wafer of gallium nitride compound, on the sapphire substrate 1 of which, an n-type GaN layer 2, a Zn doped InGaN layer 3 and a p-type GaN layer 4 are formed, is prepared. Forming a predetermined pattern of the p-type GaN layer 4, ohmic electrodes are formed on the p-type GaN layer 4 and the n-type GaN laer 2. Then masking a part of the electrode, a transparent film 5 of SnO2 is formed by deposition on the surface of the p-type GaN layer 4. The refractive index of the transparent film 5 at the wavelength of the light emission of the gallium nitride compound semiconductor is between the refractive indexes of the gallium nitride compound semiconductor and sealing material 6. Then the wafer is cut off into chips, after wire-bonding, each chip is sealed with epoxy resin, thus fabricating the light emitting elements.

Gallium nitride-based compound semiconductor light-emitting element

Abstract: PURPOSE: To make one pixel on a multicolor-luminous LED display small and to obtain a picture whose colors have been mixed uniformly even from a nearby position by a method wherein at least two active layers whose band-gap energy is different are formed in a light-emitting element CONSTITUTION: A gallium nitride-based compound semiconductor which is expressed by InXAlYGa 1- X - YN (where 0≤X≤1 and 0≤Y≤1) is laminated on a substrate 1 In a gallium nitride-based compound semiconductor light-emitting element, two or more active layers 3, 5, 7 whose band-gap energy is different are formed in the light-emitting element In the light-emitting element, the active layers 3, 5, 7 emit light when an electric current is applied to electrodes α, β, γ, δ which have been formed in individua clad layers 2, 4, 6, 8 When a prescribed voltage is applied to the individual electrodes α, β, γ, δ the individual active layers 3, 5, 7 sandwiched by the clad layes 2, 4, 6, 8 emit light As a result, colors can be mixed uniformly inside one chip COPYRIGHT: (C)1995,JPO

Deposition, characterization, and device development in diamond, silicon carbide, and gallium nitride thin films

Abstract: The extreme thermal and electronic properties of diamond, SiC, and GaN provide combinations of attributes which lead to the highest figures of merit for any semiconductor materials for high‐power, high‐temperature, high‐frequency, and optoelectronic applications. The methods of deposition and the results of chemical, structural, microstructural and electrical characterization, and device development are reviewed for thin films of these three materials. Problems and areas of future research are also noted.

Hall-effect sensor

Abstract: The invention concerns a Hall-effect sensor consisting of a multilayer structure comprising a thin semiconductor material layer deposited on a semiconductor substrate (12), the two layers being electrically insulated with an insulation. The invention is characterised in that the substrate (12) is a n+-type semiconductor material whereon is deposited an insulating material consisting of a p- type semiconductor layer (13), and the thin active layer (14) is of the n- type doped in exhaustion mode. Preferably, the active layer consists of a silicon carbide or a gallium nitride layer.

The electronic structure of gallium nitride

Abstract: The results of a density functional calculation on gallium nitride are given. We use norm-conserving pseudopotentials with sufficiently extended sets of plane waves to investigate the ground-state properties and the electronic band structure for the zincblende phase of GaN and compare them with the corresponding results for the wurtzite structure. A comparison with the outcomes of other calculations and with the existing experimental data is also given.

Gallium nitride compound semiconductor laser element

Abstract: PURPOSE: To form a P-type GaN layer and a P-type GaAlN layer, which are brought into a low resistance state evenly within their surfaces, by a method wherein the width of the waveguide of a gallium nitride compound semiconductor laser element is specified and an annealing is performed. CONSTITUTION: A GaN buffer layer 2 is formed on a sapphire substrate 1. An N-type GaN contact layer 3, an N-type GaAlN clad layer 4 and an N-type InGaN active layer 5 are each doped with Si and are formed on the layer 2. Moreover, a P-type GaAlN clad layer 6 and a P-type GaN contact layer 7 are each doped with Mg and are formed. Then, a mask is formed on the uppermost P-type Mg-doped GaN layer 7 and an etching is performed until the layer 3 is exposed to form a waveguide of a stripe width formed in a width of 50μm. After the etching, the mask is peeled from the layer 7 and an annealing is performed, whereby hydrogen gas in a semiconductor layer doped with a P-type dopant is discharged from the side surfaces of the semiconductor layer and an Mg-doped GaN layer 7 and a GaAlN layer 6, which are brought into a low resistance state evenly within their surfaces, can be formed. COPYRIGHT: (C)1995,JPO

Blue light emitting element

Abstract: PURPOSE: To provide a structure which enables high light emission output of a blue light emitting element wherein a gallium nitride compound semiconductor is used. CONSTITUTION: This the device is a blue light emitting element of a double hetero-structure which is provided with a gallium nitride compound semiconductor wherein an n-type Ga 1-a Al a N (0≤a<1) layer 3, an n-type In x Ga 1-x N (0

Gallium nitride semiconductor light-emitting device

Abstract: PURPOSE:To improve the external quantum efficiency, to eliminate a short- circuit between the electrodes of an n-type layer and a p-type layer to realize a highly reliable light-emitting device and, further, improve the reliability of a light transmitting electrode which is formed to improve the external quantum efficiency. CONSTITUTION:The electrode 4 of an n-type layer 2 and the electrode 11 of a p-type layer 3 are on the same surface side, which is to be the emitted light observing surface side, of a gallium nitride semiconductor light-emitting device. The electrode 11 of the p-type layer 3 is composed of a light transmitting first electrode 11 which is formed over the almost whole surface of the p-type layer 3 and, further, an insulating and light transmitting protective film 13 is formed on the surface of the light transmitting first electrode 11.

Gallium nitride compound semiconductor light emitting element and electrode formation thereof

Abstract: PURPOSE:To improve efficiency of outside quantum of a light emitting element and to make a gallium nitride compound semiconductor layer side a light emitting observation surface by forming a translucent electrode formed of metal in a surface of a gallium nitride compound semiconductor layer doped with p-type dopant. CONSTITUTION:A wafer which is formed by laminating a buffer layer formed of GaN, an n-type GaN layer 2 and an Mg doped p-type GaN layer 3 on a sapphire substrate one by one is prepared and the n-type GaN layer 2 is exposed by etching the p-type GaN layer 3. Then, 0.03mum-thick Ni is deposited on the p-type GaN layer 3 and 0.07mum-thick Au is deposited on the Ni. Furthermore, Al is deposited also on the exposed n-type GaN layer 2. After deposition, the wafer is annealed at 500 deg.C for 10 minutes to acquire an alloy of Ni and Au and a translucent property. The wafer is cut to a chip 350mum square and is mounted on a cup-shaped lead frame as a light emitting diode.

Study of defects in wide band gap semiconductors by electron paramagnetic resonance

Abstract: Defects in diamond, baron nitride and gallium nitride, grown by various deposition methods, were investigated by EPR measurements. In diamond films the observed EPR signal has a g value of 2.0028, peak-to-peak linewidth of 3–5 Gauss and spin-lattice relaxation time, at 293 K, of 10 -6 s. In boron nitride films, depending on growth conditions, the g value varies from 2.0024 to 2.0032, the peak-to-peak linewidth varies from 31 to 7 Gauss and the spin-lattice relaxation time at 293 K varies from 10 -5 to 10 -6 s. An EPR signal has not been observed in GaN films at temperatures above 100 K.

The method of growing indium gallium nitride semiconductor

Abstract: PURPOSE: To obtain an InGaN having good quality and crystallizability by growing an indium gallium nitride layer on a gallium nitride layer at a specific growth temperature using a nitrogen as a carrier gas of a material gas. CONSTITUTION: By using a nitrogen as a carrier gas of a material gas, a decomposition of an InGaN can be controlled at a growth temperature of higher than 600°C and even if some InN is decomposed, the InGaN with good quality can be obtained by supplying a large number of indium in the material gas. Also, by growing a buffer layer on a sapphire substrate at a low temperature before growing a GaN layer, a crystallizability of the GaN layer grown on the buffer layer is further improved and thus a crystallizability of the InGaN can be also improved. Therefore, since a semiconductor material stacked in a blue luminescent device can be formed in a double hetero structure, a blue laser diode can be implemented. COPYRIGHT: (C)1994,JPO&Japio

Gallium nitride compound semiconductor laser diode

Abstract: PROBLEM TO BE SOLVED: To connect and fix a semiconductor laser diode to a lead frame and heat sink accurately and without fail, by a method wherein a p-type electrode is connected to the exposed part of flat top of a laser resonator and formed on an insulating protective film, and an n-type electrode is formed on the second part region on the surface of a semiconductor. SOLUTION: Photoresist is uniformly applied to the upper surface of the top layer of gallium nitride compound semiconductor layer diode which is composed of a sapphire substrate 101, an n-type gallium nitride compound semiconductor layer 102, an active layer 103, and a p-type gallium nitride compound semiconductor layer 104, etc. After the photoresist is removed and an etching mask 201 is formed, they are dry-etched and the etching mask 201 is removed. Then, an insulating protective film 110 is formed on the upper exposed part of the first part region. The part where the junction part of the p-electrode 105 of a resonator flat part, and the part where an n-electrode 106 of the second part region is formed, are exposed by wet etching. Then, a p-electrode and an n-electrode 106 are formed in accordance with the prescrived treatment. COPYRIGHT: (C)1999,JPO

P-type gallium nitride

Abstract: Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5×10 11 /cm 3 and hole mobilities of about 500 cm 2 /V-sec, measured at 250° K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.