Zagoruiko Y. Modification of the physical properties of wide-band AIIBVI semiconductors for the obtaining of thermally stable elements and heterostructures for optoelectronics

The object of investigation: single crystals of AIIBVI wide-zone binary compounds and of Zn1-xMgxSe ( 0.03 ? x ? 0.60) solid solutions as well as oxide films on their surface. As investigation samples, "pure" and impurity-containing single crystals with different crystallographic orientation were used. The aim of investigation: establishment of physical foundations for modification of the optical and electrophysical properties of AIIBVI single crystals at their thermal treatment with simultaneous action of external non-thermal factors, establishment of regularities of photothermal oxidation of these crystals, obtaining of oxide coatings and Zn1-xMgxSe solid solution crystals and comprehensive study of their physical properties. Methods and equipment: thermal annealing at simultaneous action of external non-thermal factors (optical radiation, electric fields). Separate and local measurements of the absorption and scattering coefficients are performed by a modified method of adiabatic calorimetry whichallowes to investigate small optical losses within wide temperature range. The refraction coefficients are determined by the standard method of prism. The spectra of transmission in the visible and IR regions are obtained by means of spectrophotometers. The structure of the crystals and real structure defects are investigated by the method of X-ray structure analysis, optical microscopy and chemical etching. The mechanical properties of the crystals and oxide films are studied by the method of microhardness. The chemical composition of the crystals and the surface morphology are investigated by the method of scanning electron microscopy and X-ray microanalysis on electron microscope. The electrophysical properties of the samples are determined in wide temperature range by standard methods. In addition, some non-standard investigation techniques are developed. Theoretical and practical results, novelty: developed are the methods for modification of the working, optical, thermal and electrophysical parametersof AIIBVI crystals by means of their thermal treatment with simultaneous action of intense electric fields and optical irradiation. Developed and created are basic experimental technological units for realization of such kinds of thermal treatment under the conditions of pilot industrial production which provide the obtaining of thermally stable zinc selenide crystals with high optical and electrical working characteristics. Developed is a new approach to measurement and analysis of small optical losses which provides wide-range local measurements of the coefficients of IR-radiation absorption and scattering in crystalline materials for high-power IR-optics. Developed and created is the basic design for original automated unit which provides local measurements of optical absorption and scattering coefficients in crystalline ingots of optical elements of the IR-region. For the first time measured are the temperature dependences of IR-radiation absorption (at 10.6 ?m wavelength) in ZnSe and CdS single crystalsin wide temperature range (up to 750 K). The calorimetric unit "Promin" created on the base of the performed investigations was supplied to China under the license contract 02FMED84LJ4310RU. Obtained are Zn1-xMgxSe solid solution single crystals in a wide range of chemical composition changes ( 0.03 ? x ? 0.60). Determined are the concentrations of magnesium which are optimum for manufacture of thermally stable polarization and electrooptical elements for middle IR region from Zn1-xMgxSe crystals. The radiation resistance of these elements is higher than that of the traditional materials CdS, CdSe, CdS1-x,. Developed and created is an original basic design of experimental technological unit for realization and study of the processes of oxidation on the surface of semiconductor crystals. The unit allows: 1) to carry out reliable "in situ" investigations of the kinetics of oxidation processes directly at the temperatures of oxidation; 2) to obtain nano- and micro-crystalline oxide films with controlled thickness (from 80 nm to 100 ?m) and heterostructures of "oxide - semiconductor" type; 3) to investigate the processes of degradation of optical properties for semiconductor elements and devices under the action of electromagnetic and thermal fields. On the base of detailed study of the processes of photothermal oxidation in ZnSe crystals established are optimum conditions for the obtaining of structurally perfect homogeneous ZnO films of optical quality. On the base of ZnO films and heterostructures of ZnO - ZnSe, ZnO - Zn1-xMgxSe types obtained by the method of photothermal treatment, developed and manufactured are thermally stable optical, electrical and optoelectronic devices with high working characteristics: varistors, photoconverters, phototransducers as well as various optical IR-elements of transmitting type with strong interference oxide coatings. Developed and created are the samples of thermally stable multifunctional optical elements working in a wide spectral range, which combine the functions of passive optical element and sensor of continuous or modulated IR-radiation. Range of application: optoelectronics, high-power optics of middle IR-range.