Metalorganic Vapor Deposition Research Articles

Nucleation and Heterointerface Structure of InAs Epilayers Grown on InP Substrates

ABSTRACTHeteroepitaxial growth of indium arsenide films on indium phosphide substrates is being actively pursued since the electronic properties of these films make them promising materials for optoelectronic and other high speed devices. The various structural aspects of the film that affect their electronic properties are structural defects like dislocations, film-substrate interface roughness and chemical inhomogeneities. In InAs films, electrons accumulate at the film-air interface, making surface morphology an important factor that decides the electronic properties. The InAs films used in this study were grown on InP substrates by metal organic vapor deposition, at different temperatures. A higher growth temperature not only resulted in poor surface morphology of the film, but also created a rough film-substrate interface. However, at all deposition temperatures, the film-substrate interfaces are sharp. At lower growth temperature, the interfaces were flat. Films grown at lower temperatures had good surface morphology and a flat and shaip heterointerface.

Sources of donor impurities in undoped GaAs grown using arsine and trimethylgallium

Magnetophotoluminescence spectroscopy (MPL) has been used to ascertain the source of donor impurities in high-purity GaAs grown by atmospheric pressure metalorganic vapor deposition using arsine and trimethylgallium. A linear correlation between absolute MPL intensity and net carrier concentration for high-purity n-type epilayers over the concentration range 1×1014–2×1015 cm−3 provided an unambiguous method for identifying the source of donor impurities by comparing epilayers grown with different source batches. Batch-to-batch variations in the quality of films grown with eight different arsine cylinders were traced directly to the presence of varying amounts of a Ge-containing contaminant in the arsine.

Chemical vapour deposition of aluminium silicate thin films

Aluminium silicate, (Al2O3)x(SiO2)y, thin films have been grown by atmospheric pressure metal-organic vapour deposition using the volatile metal organic precusor [Al(OSiEt3)3]2. As determined by X-ray photoelectron spectroscopy, the deposited films consisted of a mixture of Al2O3, SiO2, and an aluminosilicate.

Photoluminescence characteristics of AlGaN-GaN-AlGaN quantum wells

AlxGa1−xN-GaN quantum wells were grown on basal plane sapphire by low-pressure metalorganic vapor deposition. The photoluminescence spectra of samples of different well thicknesses and x values were measured. The experimental data were compared with the calculated solutions of the finite square quantum well and the bound states involved in the optical transition were identified.

Photoluminescence study of acceptors in silicon-doped gallium arsenide grown by metalorganic chemical vapor deposition

Epitaxial silicon-doped GaAs layers were grown by metalorganic vapor deposition (MOCVD) using a silane-argon mixture as a dopant source. Two different dopant sources with silane mole fractions 2.4×10 −4 and 2.3×10 −5 were used. For both sources the electron concentration increased with the silane mole fraction in the gas flow, reached a maximum, and then fell abruptly. The maximum electron concentration was substantially higher (up to 2.1×10 19 cm −3) for layers grown with a more concentrated dopant source. The difference in silicon incorporation from different silane sources is thought to be caused by uncontrollable impurities in the diluting gas - argon. The low temperature (12 and 80 K) photoluminscence investigation revealed the presence of at least three types of acceptors in the layers: residual impurity zinc, group IV acceptors silicon versus carbon and the deep acceptor complex, silicon donor-gallium vacancy, responsible for the emission band with peak energy 1.24 eV. As a rule, this emission band was dominant in the most heavily doped layers with low electron mobilities, and its intensity was low for layers with good mobility values. Therefore the silicon donor-gallium vacancy complex is thought to be the main compensating acceptor in most heavily doped layers.

Characterization of MOCVD-grown CdMnTe films by infrared spectroscopy

Single crystal Cd1−x Mn x Te (x=0.10–0.30) films have been grown by metalorganic vapor deposition (MOCVD) on (111) GaAs substrates with and without CdTe buffer layers, at substrate temperatures of 380° to 450° C. Infrared phonon spectra reveal that the films grown at 420° C substrate temperature have reasonable Mn concentration (>10%) and are of good quality in agreement with Raman measurements. Spectral analysis also gives values for Mn concentration that agrees with photoluminescence measurements, and determines film thickness.

High-performance GaAs heterojunction bipolar transistor monolithic logarithmic IF amplifiers

Logarithmic IF amplifiers that implement both true and successive-detection designs are reported. Monolithically cascaded log gain stages are used to achieve piecewise-approximated logarithmic functions for the compression of signals over a wide dynamic range. The heterojunction bipolar transistor (HBT) IC fabrication process is based on a 3- mu m-emitter, self-aligned-base ohmic metal transistor using both molecular-beam epitaxy (MBE) and metal-organic metal vapor deposition (MOCVD) growth structures. The true log amp integrates four dual-gain (limiting and unity gain) stages without on-chip video detection. Its performance includes DC-3-GHz IF/video bandwidth, 400-ps rise time, <+or-dB log error over approximately=40-dB dynamic range at 3 GHz, and a tangential signal sensitivity (noise) of -60 dBm (test-set limited). The successive-detection log amp, designed for lower frequency and dynamic range applications, uses three limiting gain stages and four detector stages to achieve a 550-MHz bandwidth and <-0.34-dB log error over a 27-dB dynamic range. It is able to process 13-ns pulses with 5.0-ns and 5.2-ns risetimes and fall times, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photoconductive Hg1−xCdxTe detectors grown by low-temperature metalorganic chemical vapor deposition

We have fabricated high-sensitivity Hg1−xCdxTe detectors from low-temperature metalorganic vapor deposition samples. Responsivities of R=2000 V/W and detectivities of D*=2×1010 cm Hz1/2/W have been achieved.

GaAs heteroepitaxial growth on Si for solar cells

Thermal annealing effects on the reduction of dislocation density in GaAs on Si substrates were investigated. The dislocation density in GaAs films grown on Si substrates by metalorganic chamical vapor deposition was reduced by in situ thermal annealing to 2×106/cm2. We have found that the cooling and heating cycle of the GaAs film is most important factor in reducing the dislocation density in thermal annealing. Solar cells fabricated using GaAs films with 5×106/cm2 etch pit density have 18% conversion efficiency for the active area under AM1.5 simulated illumination.

First observation of quantum Hall effect in a GaInAsP-InP heterostructure grown by metalorganic vapor deposition

We report the first observation of quantum Hall effect in a Ga0.25In0.75As0.5P0.5 heterostructure grown by metalorganic chemical vapor deposition growth technique.

Degradation of GaAs lasers grown by metalorganic chemical vapor deposition on Si substrates

Using pulsed current excitation we have studied the rapid degradation of the laser properties of low-threshold-graded refractive-index single quantum well GaAs lasers grown by metalorganic vapor deposition on Si substrates. The degradation results from the growth of nonradiative regions in the active layer, resulting in rapid increase in threshold with time. The stimulated emission is quenched ∼1–5 μs after the start of the current pulse preventing continuous operation at 300 K. The degradation process is similar to that observed in similar lasers grown on GaAs substrates and occurs very rapidly due to the presence of a high density of defects and thermally induced strain.

First observation of two-dimensional hole gas in a Ga0.47In0.53As/InP heterojunction grown by metalorganic vapor deposition

We report the observation of a two-dimensional (2D) hole gas in Ga0.47In0.53As/InP heterojunction grown by metalorganic chemical-vapor deposition. In a sample with a total hole density ptot =7.6×1011 cm−2 a Hall mobility μH =10 500 cm2/V s was reached at 4.2 K. Angle-dependent Shubnikov–de Haas measurements as well as quantized Hall effect observations confirmed the two-dimensionality of the system. In contrast to the case of the 2D hole gas in GaAs/AlGaAs, low-temperature persistent photoconductivity was observed, significantly increasing the hole density at the interface.

Avalanche photodiodes with separate absorption and multiplication regions grown by metalorganic vapor deposition

InP/InGaAs avalanche photodiodes with separate absorption and multiplication regions (SAM APD's) have been fabricated from wafers grown by atmospheric-pressure metalorganic chemical vapor deposition. These APD's exhibit low dark current and good quantum efficiency. The pulse response exhibits the two-component response typical of the SAM-APD structure. The slow component is 6 ns and the fast component is 100 ps.

Rectifying GaAs-GaAlAs-GaAs structures by MOCVD compositional grading

Several graded bandgap structures have been fabricated by metalorganic vapour deposition using the GaAs-Ga1-xAlxAs-GaAs system with constant n-type doping and x varying with position. The I/V characteristics show the expected nonsymmetrical and nonlinear behaviour.

Metalorganic c.v.d. growth of GaAs-GaAlAs double heterojunction lasers having low interfacial recombination and low threshold current

Double heterostructure laser junctions have been prepared by the metalorganic vapour deposition process and evaluated for threshold current and for nonradiative recombination characteristics. Threshold currents around 850 A cm−2 were obtained, and measurements of carrier lifetime and spontaneous emission efficiency correlate well with a nonradiative lifetime of 20 ns. This value is similar to those obtained in junctions grown by liquid-phase epitaxy and puts an upper limit on interface recombination velocity of 500 cm s−1.