Deformation of single crystals of gallium arsenide

Deformation of single crystals of gallium arsenide is reported in bend and tension up to 1000° C whilst maintaining stoichiometry in an arsenic atmosphere. Surface defects and impurity segregation are shown to be dislocation sources. The dislocation density is low enough, however, to show large yield drops which are analysed in detail. Strains of 39% are possible. The activation energy for dislocation movement is increased by heat-treatment owing to an increase in point defect population.Electron microscopy shows that the predominant slip systems are {111} 110 and the majority of dislocations have b=a/2 110, the axes lying along 110 and 112 directions. Sub-cell formation occurs with sub-boundaries lying along 110 directions.     

Improvement of radiation stability of semi-insulating gallium arsenide crystals by deposition of diamond-like carbon films

We studied the properties of optical elements for the IR spectral range based on semi-insulating gallium arsenide (SI-GaAs) and antireflecting diamond-like carbon films (DLCF). Particular attention has been paid to the effect of penetrating γ-radiation on transmission of the developed optical elements. A Co⁶⁰ source and step-by-step gaining of γ-irradiation dose were used for treatment of both an initial SI-GaAs crystal and DLCF/SI-GaAs structures. It was shown that DLCF deposition essentially increases degradation resistance of the SI-GaAs-based optical elements to γ-radiation. Particularly, the transmittance of the DLCF/SI-GaAs structure after γ-irradiation with a dose 9⋅10⁴ Gy even exceeds that of initial structures. The possible mechanism that explains the effect of γ-radiation on the SI-GaAs crystals and the DLCF/SI-GaAs structures at different irradiation doses was proposed. The effect of small doses is responsible for non-monotonic transmission changes in both SI-GaAs crystals and DLCF/SI-GaAs structures. At further increasing the γ-irradiation dose, the variation of properties of both DLCF and SI-GaAs crystal influences on the transmission of DLCF/SI-GaAs system. At high γ-irradiation dose 1.4⋅10⁵ Gy, passivation of radiation defects in the SI-GaAs bulk by hydrogen diffused from DLCF leads to increasing the degradation resistance of the SI-GaAs crystals coated with DLCF as compared with the crystals without DLCF.     

Morphology- and orientation-controlled gallium arsenide nanowires on silicon substrates

GaAs nanowires were epitaxially grown on Si(001) and Si(111) substrates by using Au-catalyzed vapor-liquid-solid (VLS) growth in a solid source molecular beam epitaxy system. Scanning electron microscopy analysis revealed that almost all the GaAs nanowires were grown along <111> directions on both Si substrates for growth conditions investigated. The GaAs nanowires had a very uniform diameter along the growth direction. X-ray diffraction data and transmission electron microscopy analysis revealed that the GaAs<111> nanowires had a mixed crystal structure of the hexagonal wurtzite and the cubic zinc-blende. Current-voltage characteristics of junctions formed by the epitaxially grown GaAs nanowires and the Si substrate were investigated by using a current-sensing atomic force microscopy.     

Increasing the degradation resistance of semi-insulating gallium arsenide crystals by plasma processing

The effect of processing in hydrogen plasma on the resistance of semi-insulating GaAs crystals to degradation under the action of high-frequency (HF) electromagnetic fields and heat treatments has been studied by measuring the room-temperature IR transmission spectra of samples in a 5?C15 ??m wavelength range. It is established that the transmission of plasma-treated crystals, in contrast to untreated samples, does not decrease under subsequent HF irradiation and even increases in comparison to the initial transmission. A mechanism is proposed that explains the influence of processing in hydrogen plasma on the degradation resistance and optical transmission of semi-insulating GaAs crystals in the IR spectral range. This mechanism takes into account the relaxation of internal mechanical stresses in a near-surface layer of a crystal as a result of the plasma processing.     

Special features of the periodic-pulse-train laser radiation confinement in doped gallium arsenide and zinc selenide

Experimental data on the pulsed laser radiation confinement in compensated GaAs and ZnSe with deep impurity levels are reported for the laser wavelength λ=1.55 μm and a pulse repetition frequency of up to 100 kHz. It is demonstrated that an increase in the pulse repetition rate is accompanied by a decrease in the energy confinement threshold and by an increase in the radiation attenuation coefficient. These effects are explained by the accumulation of nonequilibrium charge carriers related to a dependence of the recombination time constant on the concentration of free impurity centers.     

Nucleation and growth of gallium arsenide on silicon (111)

The nucleation and growth of undoped gallium arsenide (GaAs) epitaxial layers, grown by metalorganic vapour phase epitaxy (MOVPE) on Si (111) substrates were investigated by transmission electron microscopy (TEM). The initial stages of epitaxial growth are considered at high and low growth temperatures. The influence of growth time and thermal annealing on the initial stages of growth are also studied and reported.     

The influence of substrate characteristics on the contact angles between liquid gallium and gallium arsenide crystals

Parameters influencing the interfacial interaction between liquid gallium and single crystalline gallium arsenide were investigated under vacuum by means of the sessile-drop technique over the temperature range ∼ 30 to 200° C. In addition to their dependence on the anisotropy of the {111} planes, contact angles in the Ga(I)/GaAs(s) system were found to be sensitive to the degree of misorientation and the direction of tilt of these planes. Furthermore, contact angles were found to be dependent on the size of the liquid drop and on the surface roughness of the substrate. In agreement with theoretical expectations the measured angles increased with increasing roughness of the GaAs surfaceS. However, these angles were found to be unaffected by the presence of N₂, Ar, and He atmospheres, and by the nature and concentration of charge carriers in the substrate.     

Temperature dependences of longitudinal ultrasonic wave propagation velocity in gallium arsenide and indium phosphide single crystals

Results are considered for experimental studies of the longitudinal ultrasonic wave propagation velocity in gallium arsenide <001> and indium phosphide <100> single crystals in the temperature range 200–355 K with measurements made through each 0.5–1 K. Measurements were made by the ultrasonic echo-pulse procedure using calibration marks of time. The frequency of the sounding signal is 10 MHz.Translated from Problemy Prochnosti, No. 11, pp. 48–49, November, 1991.     

Luminescence of bulk and thin-film single crystals of gadolinium gallium garnet excited by UV radiation

A difference between the luminescence spectra of bulk and thin-film single crystals of Gd₃Ga₅O₁₂ gadolinium gallium garnet excited by UV radiation from a deuterium lamp has been studied. The films were grown by liquid phase epitaxy from supercooled melts based on the PbO-B₂O₃ and Bi₂O₃-B₂O₃ solid solution systems.     

Damage in gallium arsenide crystals produced by ion implantation,abrasion and ball-milling

Gallium arsenide single crystals implanted with tellurium and cadmium ions at 50 and 150 keV at room temperature were examined using RHEED. Damage depth profiles were measured. Annealing was carried out to investigate the effect of temperature on the implantation damage. These effects which proved to be very complicated, included decomposition of the gallium arsenide, formation of beta gallium oxide and gallium telluride, and preferred orientation of the gallium arsenide. Comparisons were made with the annealing behaviour of ball-milled gallium arsenide using X-ray diffraction line broadening. The effects of various types of mechanical damage associated with specimen polishing of the gallium arsenide single crystals were also investigated.     

An examination of the reactive sputtering of silicon nitride on to gallium arsenide

The deposition of silicon nitride thin films by the reactive sputtering of elemental silicon in a nitrogen/argon plasma has been investigated. The composition of the thin films has been examined using infra-red reflectance, X-ray photoelectron and Auger electron spectroscopies and spark source mass spectrometry. Oxygen has been found to be a major contaminant in these sputter deposited films, the oxygen concentration depending on the ambient gas pressure. The use of the silicon oxy-nitride films as annealing encapsulants for the activation of silicon ion implanted semi-insulating gallium arsenide has also been investigated.     

Precision calibration of the silicon doping level in gallium arsenide epitaxial layers

An approach to precision calibration of the silicon doping level in gallium arsenide epitaxial layers is discussed that is based on studying the dependence of the carrier density in the test GaAs layer on the silicon- source temperature using the Hall-effect and CV profiling techniques. The parameters are measured by standard or certified measuring techniques and approved measuring instruments. It is demonstrated that the use of CV profiling for controlling the carrier density in the test GaAs layer at the thorough optimization of the measuring procedure ensures the highest accuracy and reliability of doping level calibration in the epitaxial layers with a relative error of no larger than 2.5%.     

Modification of the shape of large germanium nanoislands on silicon surface by low-energy ion bombardment

Germanium nanoislands on silicon substrates were irradiated by hydrogen and argon ions with energies below 350 eV. In the initial stage, ion bombardment leads to the division of large islands into several small islands irrespective of the ion type. The resulting surface is more homogeneous than the initial and is stable with respect to further ion irradiation.     

The role of the ohmic contact on the efficiency of gallium arsenide radiation detectors

It has recently been found that in gallium arsenide radiation detectors injecting ohmic contacts impede charge collection efficiency to get 100%, since breakdown occurs as soon as the electric field reaches the contact itself. In the present contribution, this phenomenon is investigated by comparing two sets of ohmic contacts realized by different technological procedures. While the overall defective state results to be nearly the same for both contacts, their performance significantly differs. Deep level junction spectroscopy shows that the defects are the same in both sets whilst there is much difference in density between a few of them.     

The effect of pulsed magnetic fields on the real structure of indium arsenide crystals

Experiments on InAs crystals demonstrate that exposure to pulsed magnetic fields can increase the phase homogeneity and structural perfection of the binary phases of A^IIIB^V semiconductor compounds.     

Adsorption of lithium and oxygen on gallium arsenide

The adsorption of lithium on GaAs(100) and the coadsorption of lithium and oxygen were investigated by Auger electron spectroscopy, secondary emission changes and variations in the work function ϕ. Surface treatments produced an amorphous-like substrate structure which persisted throughout the study. The lithium layer grows by the Stranski-Krastanov mode and shows a work function minimum at about 0.75–0.85 monolayers. At low lithium coverages oxygen adsorbs preferentially in “on-top” sites and so increases ϕ; at higher coverages “underneath” sites appear to be favoured and this leads to decreases in the work function. Competition between the two types of site leads to unusual dynamic effects.     

Solid-state gallium NMR characterization of cubic gallium nitride prepared by the reaction of gallium arsenide with ammonia

The reaction of cubic gallium arsenide (GaAs) with ammonia yielded gallium nitride (GaN). Powder X-ray diffraction patterns of the GaN products showed that they are a mixture of c- and w-GaN, while their Ga MAS NMR spectra revealed that they have the other phase of GaN besides c- and w-GaN and the high reaction temperature (≥900 °C) induces nitrogen deficiency in GaN. The peaks at 353 and 347 ppm in the ⁷¹Ga MAS NMR spectra were tentatively assigned to c-GaN and an intermediate of w- and c-GaN in the stacking order, respectively. The observed ⁷¹Ga chemical shifts of GaN, GaP, GaAs and GaSb in cubic phase were well correlated with the reciprocal of their band gaps.