The non-Arrhenius behaviour of Ge2Sb2Te5 conductivity is attributed to the non-linear temperature dependence of the Fermi level, assuming extended state conduction by free holes. The temperature-dependent Fermi level is shown to alter values of activation energy and prefactor for conductivity so that their exact determination becomes impossible using the conductivity data alone. However, if one assumes the temperature dependence of the Fermi level to be a parabolic function. Then, two of three model parameters can be retrieved; to obtain the third parameter one has to make an assumption about the value of prefactor for conductivity. Applying the proposed analysis scheme to Ge2Sb2Te5, reasonable values of Fermi level position are obtained and the change of Fermi level as a result of resistance drift phenomenon is demonstrated.

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It is shown that during a porous Si film formation by metal-stimulated etching a barrier layer is formed on a monocrystal p-Si substrate. The rectifying properties of the semiconductor structure can be explained by the fixation of the Fermi level in the near-surface layer of porous Si due to a high concentration of electrically active defects (deep centers or traps). It causes to energy bands bending and the appearance of a potential barrier. The study of Raman scattering showed the absence of size effects and a change in the band gap in the porous Si film. Activation energies of deep centers by the temperature dependence of the current-voltage characteristics and deep level transient spectroscopy study were determined. Keywords: porous silicon, deep level, Raman scattering, current-voltage characteristics, deep level transient spectroscopy.

It is shown that the use of both sides of solar cells created with the heterojunction technology makes possible an increase in the solar-cell efficiency. The difference in illumination of the front and back sides is associated with transformation of the blue part of the spectrum, which is shown by the example of the spectral dispersion of the quantum efficiency. The average difference between the quantum efficiency for both sides is ~11%. The short-circuit current density with the power of the solar spectrum at sea level from 400 to 1100 nm is 36.3 mA/cm 2 for the front side and 32.7 mA/cm 2 for the back side. The decrease amounts to 9.7%.