Showing papers on "Epitaxy published in 1973"

Epitaxially grown AlN and its optical band gap

Abstract: Single‐crystal layers of AlN have been grown on sapphire substrates between 1000 and 1100 °C by vapor‐phase reaction of aluminum chlorides with ammonia. The purity, color, crystallinity, growth morphology, and electrical resistivity of the epitaxial layers have been investigated. Infrared specular reflection measurements showed the presence of an appreciable strain at the AlN‐sapphire epitaxy interface. Optical absorption data strongly suggest the AlN is a direct band‐gap material with a value of about 6.2 eV at room temperature.

Work function measurements on (100), (110) and (111) surfaces of aluminium

Abstract: (100), (110) and (111) single crystal aluminium substrates were thoroughly outgassed by heating by electron bombardment in ultra high vacuum. Fresh single crystal surfaces were prepared by autoepitaxy on these substrates and the work functions of the surfaces were determined photoelectrically. The general effect of the deposition of an aluminium film on the substrate was to reduce the work function, but annealing the film at temperatures between 473 K and 573 K caused the work function to return to a constant value which was taken to be characteristic of the ordered surface. (100) aluminium surfaces were also prepared by epitaxy on potassium chloride crystals. The effect of argon ion bombardment on a bulk (110) aluminium surface is to increase the work function towards the polycrystalline value, but the characteristic value for the (110) face may be restored by annealing the crystal. There is a linear relationship between surface atom density and work function for the three faces investigated.

Epitaxial growth and piezoelectric properties of A1N, GaN, and GaAs on sapphire or spinel

Abstract: Heteroepitaxial films of the III-V compounds, A1N, GaN and GaAs have been grown on insulating substrates by reactions involving Group III metal-organic compounds and Group V hydrides. The films were examined with respect to crystallography, surface topography, uniformity, residual strain, and electrical and acoustic properties with emphasis on those orientations which are of particular interest to surface acoustic wave (SAW) device applications. Aluminum nitride films up to 10 µm in thickness were grown on 1″ diameter sapphire substrates with a 5% to 10% thickness variation. The films, though characterized as single crystal by x-ray means, exhibited a grain-like structure and considerable surface faceting. The residual strain in the films depends on the crystallographic direction and increases substantially with film thickness. These films exhibit useful surface acoustic properties. Epitaxial GaN films are more easily prepared than A1N films but by contrast are semiconducting unless “doped” with Zn or Li during the growth process. Films of this material are similar crystallographically to A1N and preliminary results show that they exhibit piezoelectric properties. The lack of published data on the acoustic properties of GaN films is probably due to the difficulty in compensating the films to provide insulating layers in device structures. Preliminary results obtained on GaAs epitaxial layers are discussed briefly because of the semiconducting properties of this material.

Growth and Characterization of Polycrystalline Silicon

Abstract: Polycrystalline silicon is deposited by pyrolysis of silane in an rf heated epitaxial reactor. The grains exhibit a fibrous microstructure having an 〈110〉 preferred orientation in the growth direction. Growth is inhibited in the presence of excess arsine and accelerated in the presence of diborane. The results are explained in terms of catalysis and poisoning of surface adsorption sites responsible for reaction. A simple model for current conduction in polycrystalline silicon is described based on grain size, grain doping, and effective barrier height due to the grain boundary. This model satisfactorily explains the observed temperature dependence of the resistivity of undoped films and also the large values of resistivity which are observed for dopant concentrations .

Acoustic surface wave properties of epitaxially grown aluminum nitride and gallium nitride on sapphire

Abstract: Experimental results are reported on the coupling of rf energy and acoustic surface waves in aluminum nitride (AlN) on sapphire and gallium nitride (GaN) on sapphire material systems. Metallized interdigital transducers are deposited on the AlN and GaN surfaces to generate and detect the acoustic surface wave energy.

Electrodes for amorphous semiconductor switch devices and method of making the same

Abstract: In a semiconductor switch device wherein upon the application of a voltage in excess of the threshold voltage value at least one current conducting filamentous path is formed of relatively low resistance, there is provided one or more electrodes comprising a single crystal of conductive material which has a smooth face contacting the amorphous semiconductor material. The single crystal electrode is preferably formed as an epitaxial layer on a single silicon chip substrate and by a process which includes vapor or sputter depositing an electrode-forming material, preferably palladium, upon the unheated exposed areas of the silicon substrate. A subsequent annealing process grows a single crystal epitaxial layer of the deposited palladium and the silicon on the substrate. The semiconductor material forming the switch device is then directly deposited on this epitaxial layer.

Properties of Epitaxial Gallium Arsenide from Trimethylgallium and Arsine

Abstract: Electrical and optical properties of epitaxial layers grown from trimethylgallium and arsine were studied by Hall and photoluminescence measurements The conduction type of the layers grown on substrates was changed from p‐ to n‐type with increase of , the mole ratio of arsine to trimethylgallium introduced, without intentional doping An emission (P2) at 1488 eV due to shallow acceptors was observed on most of the samplesCorrelations between the carrier concentration and the intensity of the P2 emission with suggest that the main acceptor impurities in the epitaxial layer are amphoteric ones on As sites, such as carbon and silicon contained in the trimethylgallium source Results of the mass‐spectrographic analysis of the layers are consistent with the above suggestion

A new method of growing GaP crystals for light-emitting diodes

Abstract: A method named synthesis, solute diffusion (SSD) has been developed for growing compound semiconductor crystals, GaP in particular, for light-emitting diode (LED) use. The grown crystal is cylindrically shaped and is composed of fairly large-size grains. Growth rate is limited by the diffusion process of phosphorus in the gallium melt. The diffusion coefficient was obtained from the growth rate and found to be 8×10-5cm2s-1at 1100°C with an activation energy of 0.65 eV. Donor impurities, tellurium or sulfur, can be reproducibly incorporated from 3×1017to 4×1018cm-3, with segregation coefficients at 1150°C, 0.038 and 1.0, respectively. The quality of the grown crystals was observed to be exceptionally good, and the saucer-type pits were hardly observable in the crystal on modified AB etching. Highly efficient red-light-emitting junctions were reproducibly grown by only one single-layer-single-liquid-epitaxy process, in which zinc was doped from the vapor phase. A double-layer-single-epitaxy process, which we call "liquid epitaxial grown-in junction" process, was also developed and it produced highly efficient green LED's. The LED's grown on the SSD wafers have efficiencies up to 7.4 percent for red and 0.15 percent for green.

Epitaxial growth of silicon from SiH4 in the temperature range 800–1150°C

Abstract: Results on the deposition of silicon from SiH 4 are reported for a temperature range 800–1150°C. Deposition was carried out at atmospheric pressure and at reduced pressures in the range 0·2-1 Torr where it was possible to maintain an h.f. glow discharge in the reactor tube. Using the h.f. discharge good quality epitaxial growth was achieved at 800°C for both undoped and heavily doped n -type layers. The main advantage of using the discharge is thought to be the marked cleanup it gives to the substrate prior to deposition taking place.

Measurement of carrier-concentration profiles in epitaxial indium phosphide

Abstract: A technique is described for measuring carrier-concentration profiles of vapour-deposited epitaxial indium phosphide using the capacitance/voltage characteristics of a reverse biased metal-insulator-semiconductor diode. Profiles of layers grown on chromium and tin-doped substrates are presented. The effect of dopant type on the sharpness of electrical interfaces is discussed.

Velocity of domain walls in an epitaxial yttrium‐europium garnet film

Abstract: Measurements of magnetic domain velocity by domain transport methods in an epitaxial Y2.4Eu0.6Ga1.2Fe3.8O12 film have yielded values as high as 2800 cm/sec with no sign of saturation. These measurements conflict with those reported recently by Callen et al., who deduced a saturation velocity of 1300 cm/sec from bubble collapse measurements made on films of the same composition. It is suggested that the discrepancy is due to the wall velocity reaching momentarily the Walker breakdown velocity in the bubble collapse technique, which then leads to a relatively immobile spin configuration similar to the one reported recently for hard magnetic bubbles.

Vapor‐Doped Multislice LPE for Efficient GaP Green LED's

Abstract: A single‐step liquid phase epitaxy process has been developed for the growth of efficient green light‐emitting diodes (LED's), in which all doping is accomplished from the vapor phase. The use of vapor‐phase doping increases the flexibility of the LPE process since junction formation and control of doping profiles is accomplished by regulating the composition and flow rates of the doping gases. This method has been applied to multislice growth on large area substrates (up to 38 mm in diameter). Thin melts and nearly complete utilization of the GaP initially dissolved in the melt minimize the gallium usage. Encapsulated LED's with efficiencies in the 0.10–0.15% range at 7 A/cm2 are obtained routinely. These efficiencies are comparable to the highest values reported to date for low current operation. Efficiencies as high as 0.2% have been obtained at 7 A/cm2 using this method. The short deposition time for this single‐step method, reproducibility, multislice capability, and minimum gallium consumption make this method economically attractive for the high level production of efficient green LED's.

The electrochemical characterization of n-type gallium arsenide

Abstract: A method for determining the carrier concentration of n-type gallium arsenide by an electrochemical technique is described. The minority carrier diffusion length is also obtained, and using subsidiary measurements the minority carrier lifetime can be estimated. The extension of this treatment to the characterization of epitaxial layers is discussed.

Method and apparatus for production of liquid phase epitaxial layers of semiconductors

Abstract: Single-crystal epitaxial layers of compound semiconductors or mixed semiconductors are grown on suitable substrates from the liquid phase, which consists of a molten metallic solvent dissolving a source material of the semiconductors, and within which the temperature gradient is produced so that in a high temperature region of the liquid solution a solid source material is dissolving into the liquid solution with at least a portion of the solid source material always at an undissolved state and in a low temperature region of the liquid solution an epitaxial layer is depositing onto the substrate, the temperatures in the liquid solution being kept constant during the epitaxial growth. Each substrate is positioned in one of a number of slots which are provided in the upper surface of a slider and it is successively transferred with the slider to contact with the liquid solution. The composition and/or the doping level of each epitaxial layer are controlled by the composition and/or the doping level of the solid source material which is selected from a pre-synthesized material, i.e., a solid film produced on the liquid solution by supersaturation and a film deposited on the liquid solution from the vapor phase.

Semiconductor device having an insulating layer of boron phosphide and method of making the same

Abstract: A semiconductor device having an insulating layer made of boron phosphide which is epitaxially deposited on a silicon substrate as a first layer. A silicon layer is epitaxially deposited on the first epitaxial layer as a second layer. In this case, integrated circuits are formed in the second epitaxial layer the electronic elements of which are electrically isolated with one another and the second epitaxial layer is also electrically isolated from the silicon substrate by the first epitaxial layer made of boron phosphide which shows high electrical resistance. Further, a method of fabricating a semiconductor device having a step of depositing an epitaxial layer of boron phosphide on a silicon substrate.

Low-temperature epitaxy of Ge films by sputter deposition

Abstract: It is shown experimentally that isoepitaxial growth of Ge films on Ge substrates can be obtained by dc sputtering at substrate temperatures as low as 100 C. The crystallographic structure and orientation of the films are strongly influenced by such deposition parameters as substrate temperature, growth rate, surface contamination, and sputtering-gas purity. The amorphous-polycrystalline transition occurs between 110 and 115 C, while the polycrystalline-single crystalline transition occurs at roughly 140 C. The crystallographic order increases with increasing substrate temperature.

Hetero-Epitaxial Growth of Lower Boron Phosphide on Silicon Substrate Using PH 3 -B 2 H 6 -H 2 System

Abstract: Single crystal of lower boron phosphide (B13P2) with hexagonal structure was obtained hetero-epitaxially on silicon substrate. Diborane (B2H6) and phosphine (PH3) diluted in hydrogen were used as reactant gases. The substrate temperatures were between 1050°C and 1250°C and the molecular ratio of reactants to carrier hydrogen was below 3.2×10-4. The epitaxial relations were: B13P2(110)/Si(100), B13P2(110)/Si(110) and B13P2(100)/Si(111). The lower boron phosphide was a transparent film and its resistivity was measured as 1×108 Ω-cm at room temperature.

Epitaxial Growth and Characterization of Pyrolytic‐Grown GaAs1 − x P x for Electroluminescent Diodes

Abstract: Epitaxial layers of on substrates were prepared using trimethylgallium, arsine, and phosphine. The growth was primarily mass transport limited and the phosphorus content in the layers increased linearly with the phosphine content in the vapor and the substrate temperature. Growth pyramids appeared at high phosphine content in the vapor and were brighter than flat regions in the cathodoluminescent image. A diode, fabricated by diffusing zinc into layers, showed brightness of 43 ft‐L at 8 A/cm2 with an external quantum efficiency of about 0.01%. The external efficiency has been found to depend strongly on the generation‐recombination current and the deep level impurity concentration in the depletion layer.

Process for forming monolithic semiconductor display

Abstract: A process for producing light emitting diodes is disclosed. In the process a major planar surface of a single crystal silicon wafer is modified to acceptably match the crystallographic lattice constant of a preselected electroluminescent single crystal semiconductor, such as gallium phosphide. The preselected electroluminescent semiconductor material is then epitaxially deposited in single crystal form on the modified surface of the silicon wafer, a step which is not feasible without the modification of the silicon wafer surface. Preferably, the modification is achieved by epitaxially depositing a thin layer of semiconductor material whose lattice structure offers, a substantially smaller disparity with the structure of the electroluminescent material than the existing disparity between the silicon wafer and the electroluminescent material.