http://dspace.nbuv.gov.ua:80/handle/123456789/114589 2026-04-19T04:41:33Z 2026-04-19T04:41:33Z Kosyak, V.V. Opanasyuk, A.S. http://dspace.nbuv.gov.ua:80/handle/123456789/118133 2017-05-29T00:05:24Z 2007-01-01T00:00:00Z

Calculation of Fermi level location and point defect ensemble in CdTe single crystal and thin films Kosyak, V.V.; Opanasyuk, A.S. With the use of expressions obtained from the “first principles”, the ensemble of point defects was calculated, and the location of a Fermi level in undoped cadmium telluride single crystals and thin films depending on physico-technological conditions of their fabrication and annealing is determined. The model in use accounts the most complete spectrum of defects in chalcogenide, including defects in the cadmium and tellurium sublattices, and the existence of an antistructural defect on the cadmium sublattice. Calculations of the concentration of neutral and charged defects are realized for two extreme cases – full equilibrium and quenching. The comparison of the obtained results with the data of modeling provided with the use of a quasichemical formalism for a number of models most used presently is carried out. It is shown that all models describe well the results of Hall measurements of the concentration of free carriers in single crystals in the range of high cadmium pressure, but give essentially different results in the range of high tellurium pressure. Dominant defects in single crystals at high cadmium pressure and annealing temperatures are twice charged tellurium vacancies or interstitial cadmium atoms, which is in agreement with experimental results, as just such defects can provide the dependence of the concentration of free carriers on cadmium pressure as n ~ P¹/³Cd . A type of defects which are dominant in a tellurium-enriched material is determined by the chosen model. This allows us to make conclusions about the validity of the considered models and to specify the thermodynamic parameters of the defect creation processes in a material. The offered model can be used for modeling the ensemble of point defects in any А₂В₆ compounds. Thus, the problem of the choice of models adequate to experimental data is reduced to the determination of the creation energy for uncharged defects and the depth of energy levels of charged defects.

2007-01-01T00:00:00Z Danilyuk, A.I. Dobrovolskiy, Yu.G. http://dspace.nbuv.gov.ua:80/handle/123456789/118132 2017-05-29T00:04:09Z 2007-01-01T00:00:00Z

Estimation on frequency characteristics of a photodiode determined by the motion of charge carriers in the region of volume charge on the surface generation of carriers Danilyuk, A.I.; Dobrovolskiy, Yu.G. We have estimated the frequency characteristics of a photodiode determined by the motion of charge carriers in the space-charge region on the surface generation of carriers in two extreme cases of unalloyed and evenly alloyed semiconductors. The expressions allowing the comparison of photodiodes with different constructions have been obtained.

2007-01-01T00:00:00Z Vlasenko, N.A. Oleksenko, P.F. Denisova, Z.L. Mukhlyo, M.A. Veligura, L.I. http://dspace.nbuv.gov.ua:80/handle/123456789/118131 2017-06-06T13:59:34Z 2007-01-01T00:00:00Z

Thermofield Cr→Cr²⁺ recharging resulting in anomalous intensification of Cr²⁺ emission in ZnS:Cr thin-film electroluminescent structures Vlasenko, N.A.; Oleksenko, P.F.; Denisova, Z.L.; Mukhlyo, M.A.; Veligura, L.I. For the first time, an anomalous strong increase of the Cr²⁺ emission intensity (I) with increasing the applied voltage (V) has been discovered in ZnS:Cr thin-film electroluminescent structures (TFELS) instead of the I(V) dependence saturation typical of TFELS of the MISIM type, where M is an electrode, I is an insulator layer and S is an EL film. The dependence of I on the transferred charge (Q) is very superlinear, whereas the luminance of the emission of hot electrons, which takes place simultaneously with the Cr²⁺ emission, increases proportionally to Q as it happens usually in TFELS. The increase of I and Q is accompanied by rising the sample temperature up to 30 – 50 °C. However, the emission spectrum that is inherent to the ⁵E → ⁵T₂ transition in the 3d shell of a Cr²⁺ ion is not changed in this case. The above effects are explained by Cr⁺ → Cr²⁺ thermofield recharging, which results in an increase of the number not only of free electrons, but also of Cr²⁺ radiation centers. The most probable mechanism of such a recharging is the Frenkel-Pool field-stimulated thermal ionization of Cr⁺ ions, whose ionization energy is 0.65…0.82 eV.

2007-01-01T00:00:00Z Kaminskii, V.I. Kovalyuk, Z.D. Netyaga, V.V. Boledzyuk, V.B. http://dspace.nbuv.gov.ua:80/handle/123456789/118130 2017-05-29T00:03:34Z 2007-01-01T00:00:00Z

Dielectric characteristics of GaSe nanocrystals intercalated with hydrogen Kaminskii, V.I.; Kovalyuk, Z.D.; Netyaga, V.V.; Boledzyuk, V.B. The results of investigations of dielectric characteristics of GaSe nanocrystals and their hydrogen intercalates are presented. By using the impedance spectroscopy method, it is established that the dielectric spectra of GaSe and HxGaSe (х = 0.07 and 0.14) nanocrystals correspond to the exponent law of dielectric response. It is found that there is an increase of the dielectric constant ε∞ for the intercalated samples in comparison with that of the initial sample. We have obtained the frequency dependences of the real and imaginary parts of the conductivity, whose dispersion is due to the presence of two-dimensional defects. Equivalent electrical circuits which determine electrical characteristics of the crystals under study are proposed.

2007-01-01T00:00:00Z