Semicond. Physics Quantum Electronics & Optoelectronics, 2007, № 3http://dspace.nbuv.gov.ua:80/handle/123456789/1145892024-03-28T20:47:17Z2024-03-28T20:47:17ZCalculation of Fermi level location and point defect ensemble in CdTe single crystal and thin filmsKosyak, V.V.Opanasyuk, A.S.http://dspace.nbuv.gov.ua:80/handle/123456789/1181332017-05-29T00:05:24Z2007-01-01T00:00:00ZCalculation 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.
2007-01-01T00:00:00ZEstimation on frequency characteristics of a photodiode determined by the motion of charge carriers in the region of volume charge on the surface generation of carriersDanilyuk, A.I.Dobrovolskiy, Yu.G.http://dspace.nbuv.gov.ua:80/handle/123456789/1181322017-05-29T00:04:09Z2007-01-01T00:00:00ZEstimation 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.
2007-01-01T00:00:00ZThermofield Cr→Cr²⁺ recharging resulting in anomalous intensification of Cr²⁺ emission in ZnS:Cr thin-film electroluminescent structuresVlasenko, N.A.Oleksenko, P.F.Denisova, Z.L.Mukhlyo, M.A.Veligura, L.I.http://dspace.nbuv.gov.ua:80/handle/123456789/1181312017-06-06T13:59:34Z2007-01-01T00:00:00ZThermofield 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.
2007-01-01T00:00:00ZDielectric characteristics of GaSe nanocrystals intercalated with hydrogenKaminskii, V.I.Kovalyuk, Z.D.Netyaga, V.V.Boledzyuk, V.B.http://dspace.nbuv.gov.ua:80/handle/123456789/1181302017-05-29T00:03:34Z2007-01-01T00:00:00ZDielectric 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