Influence of Substrate Misorientation on the Composition and the Structural and Photoluminescence Properties of Epitaxial Layers Grown on GaAs(100)

The influence of the degree of misorientation and treatment of a GaAs substrate on the structural and optical characteristics of homoepitaxial GaAs/GaAs(100) structures grown by metal–organic chemicalvapor deposition is studied. From the data obtained by a series of structural and spectroscopic techniques, it is shown that the degree of deviation of the substrate from the exact orientation towards the [110] direction by an angle of up to 4° brings about stepwise growth of the GaAs film in the initial stage and a further increase in the degree of misorienration towards the [110] direction to 10° results in an increase in the number of structural defects in the epitaxial film. At the same time, the samples of homoepitaxial structures grown by metal–organic chemical-vapor deposition on GaAs(100) substrates misoriented by 4° towards the [110] direction possess the highest photoluminescence efficiency; it is ~15% higher than the corresponding quantity for structures grown on precisely oriented GaAs(100) substrates. Preliminary polishing of the GaAs substrate (removal of an oxide layer) also yields the intensification of photoluminescence emission compared to emission in the case of an unpolished substrate of the same type. For samples grown on substrates misoriented by 4°, such an increase in the photoluminescence efficiency is ~30%.     

Variations of temperature in specimens of rocks and geomaterials under failure

Loading causes stress concentration around defects in rocks, which induces initiation and propagation of cracks. Physically, external loading shows itself in rocks as acoustic and electromagnetic emission, included infrared radiation. Experimentally, it is found that in specimens of geomaterials under uniaxial tension, temperature is minimum; under uniaxial compression, temperature grows; under triaxial stress, temperature is maximum. It has been succeeded to derive equations for temperature prediction in a material in the zone of main crack as function of failure load. The method to estimate stress state based on the data on infrared radiation in materials is developed.     

Phase formation under the effect of spinodal decomposition in epitaxial alloys of Ga x In1 − x P/GaAs(100) heterostructures

The effect of instability of alloys of Ga _x In_{1 − x} P/GaAs(100) semiconductor epitaxial heterostructures in the composition region x ≈ 0.50 is studied by X-ray diffraction and electron microscopy. The possibility of emergence of modulated relaxation structures on the surface of a Ga _x In_{1 − x} P alloy is shown. This phenomenon is accompanied by the emergence of satellites of main X-ray reflections corresponding to a single-phase structure.     

Structural and optical properties of GaAs(100) with a thin surface layer doped with chromium

The aim of this study is to explore the structural and optical properties of single-crystal GaAs(100) doped with Cr atoms by burning them into the substrate at high temperatures. The diffusion of chromium into single-crystal GaAs(100) substrates brings about the formation of a thin (~20–40 μm) GaAs:Cr transition layer. In this case, chromium atoms are incorporated into the gallium-arsenide crystal lattice and occupy the regular atomic sites of the metal sublattice. As the chromium diffusion time is increased, such behavior of the dopant impurity yields changes in the energy structure of GaAs, a decrease in the absorption at free charge carriers, and a lowering of the surface recombination rate. As a result, the photoluminescence signal from the sample is significantly enhanced.     

Porous silicon nanoparticles containing neurotropic drugs

Porous silicon samples with a pore diameter under 100 nm have been prepared by a two-sided anodic electrochemical etching of single-crystal silicon. We have studied vinpocetine and afobazol sorption on porous silicon. The drugs have been shown to have no effect on the structure of the porous silicon. Comparison of the degree of afobazol and vinpocetine release from the drug delivery systems produced in this study and from microcapsules demonstrates that porous silicon nanoparticles can be used as a means of prolonged drug delivery, suggesting that further pharmacological research is warranted.     

Structural and Morphological Properties of Hybrid Heterostructures Based on GaN Grown on a Compliant por-Si(111) Substrate

Semiconductors - The possibility of synthesizing integrated GaN/por-Si heterostructures by plasma-assisted molecular beam epitaxy without an A1N/Si buffer layer is demonstrated. The beneficial...     

Investigation into the Influence of a Buffer Layer of Nanoporous Silicon on the Atomic and Electronic Structure and Optical Properties of AIIIN/por-Si Heterostructures Grown by Plasma-Activated Molecular-Beam Epitaxy

Semiconductors - The influence of using a buffer sublayer of nanoporous por-Si on the morphological, physical, and structural properties of nanocolumnar InxGa1 –xN structures fabricated by...     

Influence of a Nanoporous Silicon Layer on the Practical Implementation and Specific Features of the Epitaxial Growth of GaN Layers on SiC/por-Si/c-Si Templates

Semiconductors - A set of structural and spectroscopic methods of diagnostics is used to study the influence of a nanoporous silicon (por-Si) transition layer on the practical implementation and...