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The transport properties of 6GaAs (Si) at high temperatures were studied using the 'mobility spectrum' technique. Strong changes in the subband occupancies were observed in a low-doped sample (No = 1.5 x 10'2cm-2) as the temperature increased from 77 K to 300 K while in a high-doped sample (ND = 5.0 x 1'0'~cm-~) these changes were small. For an explanation of the observed behaviour with temperature Poisson's and Schrddinger's equations were solved self-consistenti y. independent of temperature while the mobilities of the higher subbands (i > 0) decreased with increasing temperature in both IOW-and highdoped samples. At 'close to room temperature, the conductivity of the &structures can be described well by a two-carrier model where the first group of carriers consists of the electrons of t h e lowest subband and the second group consists of the electrons of all the higher subbands having approximately equal mobilities.The mobility of the lowest subband (i = 0) was found to be relatively

A method of scanning photodielectric spectroscopy of crystals has been suggested. It is based on the measurements of small increments of the real Δε′ and imaginary Δε″ parts of effective dielectric permittivity at a smooth variation of the photoexcitation wavelength λ. The spectral functions Δε′(λ) and Δε″(λ) are presented in a complex plane, that is, in parametric view, and their characteristic points are determined. Application of this method on Cd1−xZnxTe crystals showed a possibility of determining the energy position of the localized states generated in the forbidden zone by the intrinsic structure defects.