Establishment of specific features of electron localization at U- centers in semiconductors from thermally stimulated currents

The specific features of thermally stimulated currents in semiconductors containing U- centers are treated theoretically in comparison with the corresponding features for semiconductors containing defects with a positive correlation energy or single-level centers. It is shown that the analysis of the curves of thermally stimulated currents normalized to the maximum current in respect to the shape and to the presence or absence of a shift of the temperature maximum of the curve in relation to the initial occupancy provides an extra necessary criterion for identifying defects with different parameters of binding of electrons. The results can be used in analyzing experimental data on thermally stimulated currents that exhibit features inexplicable in the context of the often used model of single-level centers.