Investigation of electronic kinetic processes in solid state material and especially in semiconductors has great importance because it provides information about the main fundamental characteristics of the material such as energy level structure, relaxation processes, Fermi surface shape, volume charge distribution, specific properties of charge carriers, etc. These parameters can be measured both using electrical and optical methods. The latter are preferable because they allow nondestructive testing of materials to be carried out. The dynamics of space-charge fields in wide-gap high-resistive materials is very slow (the Maxwell relaxation time is inversely proportional to the conductivity of the material). Utilization of conventional methods for the characterization of material parameters, for example, photoconductivity of the material, is difficult due to the influence of the internal space-charge field on the results of the measurement. There are two modern techniques for wide-gap materials investigation.of such measurements.
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