Electrical and luminescent properties of near−UV light emitting diode structures (LEDs) prepared by hydride vapor phase epitaxy (HVPE) were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates) of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure.

The problem of obtaining crystalline ZnSe doped with d-elements for obtaining high-efficiency laser materials with characteristics in a wide IR range don’t possible successfully solved without reliable data on phase equilibrium and solubility of the components entering the system. The theoretical and experimental analysis of the three-component Zn—Se—Fe system for obtaining new fundamental information on phase using X-ray analysis (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) was carried out. New experimental data of isothermal annealing in the ternary Zn—Se—Fe system at the temperatures 730 K (I, II), 814 K (III, IV), 1073 K (V), as well as information on Fe solubility in bi- and monovariant conditions by X-ray studies have shown the existence of the coexistence of the following phases: Fe3Zn10-Fe11Zn40-Zn-ZnSe (I), ZnSe-FeSe2-Fe7Se8 (II), ZnSe-Fe3Zn10-Fe (III), FeSe2-Fe7Se8-Se (IV), ZnSe-FeSe- Fe3Se4 (V), ZnSe-FeSe (VI) and confirmed the reliability of theoretical isothermal sections.

Bidomain single crystals of lithium niobate (LiNbO₃) and lithium tantalate (LiTaO₃) are promising material for usage as actuators, mechanoelectrical transducers and sensors working in a wide temperature range. It is necessary to take into account anisotropy of properties of crystalline material when such devices are designed. Inthis study we investigated deformations of bidomain round shaped Y + 128°-cut wafers of lithium niobate in an external electric field. Dependencies of piezoelectric coefficients on rotation angles were calculated for lithium niobate and lithium tantalate and plotted for the crystal cuts which are used for bidomain ferroelectric structure formation. In experiment, we utilized external heating method and long-time annealing with lithium out-diffusion method in order to create round bidomain lithium niobate wafers. In order to obtain dependencies of the bidomain crystals’ movements on the rotation angle with central fastening and external electric field application optical microscopy was used. We also modeled a shape of the deformed bidomain wafer with a suggestion that the edge movement depends on the radial distance to the fastening point quadratically. In conclusion, bidomain Y + 128°-cut lithium niobate wafer exhibits saddle-like deformation when DC electric field is applied.

When the refractive index changes very slowly compared to the wave-length we may use the eikonal approximation to the wave equation. In the opposite case, when the refractive index highly variates over the distance of one wave-length, we have what can be termed as the anti-eikonal limit. This situation is addressed in this work. The anti- eikonal limit seems to be a relevant tool in the modelling and design of new optical media. Besides, it describes a basic universal behaviour, independent of the actual values of the refractive index and, thus, of the media, for the components of a wave with wave-length much greater than the characteristic scale of the refractive index.

In the paper a new approach to solve the optimization problem of nanoscale semiconductor heterostructures is presented. In this paper the authors formulated and solved The problem of the barrier layer optimal doping is formulated for the case of multilayer barrier. The problem is solved using the effective optimization algorithms based on gradient methods. As an example, is considered heterostructure Al0.25GaN/GaN with the total thickness of the barrier layer 30 nm. Obtained in the computational experiment results are consistent with the modern trend to move from homogeneous doping profile to a planar-doping in the technology of manufacturing fieldeffect transistors. The developed tools of mathematical modeling and optimization can be used in the engineering of field effect transistors. The proposed approach creates the conditions for computer-aided design of such structures.

A complex of studies of the AlGaN/GaN heterostructures and the AlGaN/GaN/SiC HEMT-transistors Schottky barriers has been carried out by the C-V method and the SIMS method in order to determine the causes of the capacitance instability in some cases was made. It is shown that in most cases, the appearance of a capacitance peak on the C-V curves at frequencies 20-500 kHz was associated with the presence of leakage currents in the barrier layer and at low frequencies 1-20 kHz with generation-recombination centers.

We have tested the possibility of using monomolecular layers of bacteriorhodopsin (BR) for the synthesis of highly sensitive and highly selective sensors based on second harmonic generation and surface plasma waves. We have used various methods to study the optical and nonlinear optical properties of Langmuir-Blodgett films of BR in order to clarify the extent to which specific properties of BR molecules are retained during their transfer from the surface of water to a solid substrate. We show that the second harmonic generation method is efficient for analyzing the molecular orientation and quality of Langmuir-Blodgett films. The experimental nonlinear optical susceptibility of second order BR molecules is 3.4 · 10^-11 m/V. The relative change in the resonant wave vector is (3.6 ± 0.1)·10^-2 at an excitation light wavelength of 630 nm. We have obtained a BR spectrum with the effective excitation by incident radiation of surface plasma waves. On the basis of these studies, we have proposed new schemes of biosensors operating on the basis of second harmonic generation and surface plasma resonance caused by fundamental frequency reflection from BR monomolecular layers. This scheme was tested for a model device and demonstrated the possibility of obtaining sensitivities of the order of 10¹¹ molecules/cm³.

Based on the analysis of numerous experimental data shows that the generally accepted today, the glass transition temperature Tg is not. It was the result of borrowing from tammana symbol Tg, is meant the temperature of viscous flow liquid transformation into solid brittle glassy state, and use it together symbol Tw, means the temperature tammana bend on the dependence of the «property-temperature» glass-forming substances above Tg of tammana. On the basis of the application of polymer-polymorphing representations of the structure of glass-forming substances are disclosed physico-chemical nature of the temperature curve Tw (conventional Segodnya), which is the temperature of the reverse direction interconversion of nanofragments patterns (polymorphical) high and low temperature polymorphs that coexist in the vitreous substance. The discovery in recent decades prezentatsionnogo effect located as tammana Tg, is below the standard Tg, Tg confirms the truth of tammana characterized by increasedspecific heat of the heated glass.