Distribution of silicon over sublattices in semiconducting A3B5 compounds

The stable site of Si substitutional impurities in GaAs and AlAs at T=0 K is determined on the basis of an analysis of the energy of solution of silicon, and of the energies of formation of intrinsic defects and the reaction energies of their interaction obtained by calculating the total energy of the disordered compounds. These calculations indicate that amphotericity and vacancies have an effect on the distribution of Si. At low Si concentrations, Si in GaAs is located on the sublattice of the group III element, and in AlAs, on the sublattice of the group V element. Fiz. Tverd. Tela (St. Petersburg) 39, 264–266 (February 1997)     

Nature and singularities in the behavior of point defects in doped single crystals of A3B5 compounds

Conclusion In conclusion, It should be stressed that, as follows from the experimental material considered, a characteristic singularity of semiconductor compounds is the stability of the metastable state which occurs during dissociation of the supersaturated solid solution under relatively small supersaturation conditions. The defects being formed here (interstitial atoms, vacancies, their distinct association in the form of complexes or coagulated particles, presegregated, etc.) exert considerable influence on the physical properties of crystals. In the general case, the crystal defectiveness depends on the kind and concentration of the doping impurity, the deviation of the composition from stoichiometry, and the ingot cooling mode during growth.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 7–22, January, 1980.     

Reradiation effects,lifetimes and probabilities of band-to-band transitions in direct A3B5 compounds of GaAs type

A determination has been made of the efficiency and decay time of edge emission for some direct band-gap A₃B₅ semiconductor compounds (the active region of matched heterostructures) with the reradiation effect being taken into account. It has been established that the lifetime of minority carriers is due to band-to-band radiative transitions, the rate of which correspond to the simple quantum-mechanical theory.     

Sonolytic degradation of halogenated organic compounds in groundwater: mass transfer effects

Organic pollutants in liquid exposed to acoustic waves behave differently according to their physical and chemical properties. Laboratory batch experiments of sonication for the degradation of trichloroethylene (TCE) and ethylene dibromide (EDB) were carried out in groundwater at 20 kHz, and 12.5 and 35 W/cm(2). A theoretical model for the batch sonication system was derived to examine the mass transfer dependency of the ultrasonic degradation. Experimental results were supported with model predictions suggesting that both liquid phase diffusion coefficient and Henry's law constant are important parameters for the sonolytic degradation of the halogenated organic compounds in groundwater. When compared with the effect of the diffusion coefficient, Henry's constant exerts a greater influence on sonolytic degradation. When Henry's constant exceeds a value of 1 (volume/volume ratio), however, it no longer has much influence on the degradation process. The results also suggest that degradation is enhanced with an increase in ultrasonic power probably due to a greater bubble residence time and the formation of larger bubble at high-energy intensities.     

Reordering kinetics of disordered A15 compounds

The study of reordering in A15 compounds gives valuable information about atomic processes in this structure. This information is relevant to diffusion and solid-state compound growth, as well as to recovery from radiation damage. It also offers further valuable insight into the nature of radiation damage in these materials, complementing the results obtained by X-ray studies, electron microscopy, and the measurement of superconducting and normal-state properties. The extreme sensitivity of superconducting critical temperature T_c to the degree of order in the A15 compounds allows the former property to be used to monitor the reordering- process. The recovery of T_c in A15 compounds disordered thermally and by neutron irradiation has been achieved by annealing, and the data analyzed in terms of a theory of reordering due to Welch. From this analysis, it is possible to make estimates of the activation energies for atomic migration and vacancy formation in A15 compounds.     

Band structure of electronic levels and the formation of the fluorescence spectra of polar compounds in polar media

The paper sets out a statistical theory of the effect exerted by interactions of constant dipoles in solutions on the fluorescence spectra of polar compounds. The theory is based on the concept of band structure of the electronic levels of a polar impurity (dissolved) molecule in polar media. Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 209–216, March–April, 1997.     

Influence of growth conditions on the surface quality and structural perfection of multicomponent heterostructures based on group A3B5 compounds

The surface quality of epitaxial multicomponent layers based on group A³B⁵ compounds, which are grown under different conditions via floating-zone refining with a temperature gradient, is comprehensively analyzed. The main parameters (temperature gradient, solution-melt composition, supercooling level, matching between lattice parameters and the thermal expansion coefficients of the layer and substrate, and substrate orientation) affecting the surface quality and structural perfection of the heterostructures are determined.     

Thermodynamical foundations of the technology of the semiconducting compounds A2B4C2 5

For the semiconducting compounds A²B⁴C₂ ⁵ (A²-Cd and Zn; B⁴-Sn and Ge; C⁵-As and P) complex thermodynamical evaluations are carried out of technologically important parameters. Using models of multicomponent simple and regular solutions, liquidus temperatures are determined near the point of the triple compound, equilibrium partial pressures are computed of pairs of components,a priori evaluations are carried out of thermodynamical parameters of characteristic structural defects and, starting from the analysis of processes of defect-formation in the semiconductors under consideration, their homogeneous regions are evaluated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 40–51, October, 1993.     

A3B5 nanowhiskers: MBE growth and properties

The structural properties of GaAs nanowhiskers (NWs) grown by molecular beam epitaxy (MBE) are investigated. Under optimal growth conditions, the aspect ratio of MBE grown GaAs NWs is higher than 100. The maximum length of NWs is several times (up to 10) larger than the effective thickness of deposited GaAs. A kinetic model of the diffusion-induced NW rowth is used to predict the dependence of NW length on the technologically controlled MBE growth conditions. The obtained results demonstrate that the NW growth is controlled by the adatom diffusion towards their tip rather than by the conventional vapor-liquid-solid mechanism. The growth conditions influence on the NW morphology may be used for the controlled fabrication of NWs by MBE for different applications. Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005.     

Optical determination of the charge transfer in AsF5-graphite intercalation compounds

Optical reflectance experiments are performed on well-characterized compounds C_8nAsF₅ (n = 1, 2), in the temperature range 10–300 K. The theoretical analysis of the reflectivity spectra within the 2-D model of graphite independent subsystems [1] provides an optical determination of E_F and the charge transfer coefficient which is found independent of temperature.