Electronic properties and energy spectrum of SnTe doped with In

The temperature and concentration dependences of electrical conductivity (sigma) , Hall coefficient RH and coefficient of thermo-e.m.f. S for the samples of the SnTe solid solutions are obtained. On the basis of experimental data the model of energy spectrum of SnTe doped with In taking into account the high concentration of nonstoichiometric vacancies in SnTe and variable valency of the In atoms is proposed. According to the model the valence band contains tow resonance bands corresponding to the In atoms localized in octa- and tetrahedral positions. The vacancy band is the lowest on the energy scale of the valence band, followed by impurity bands. The gaps and their temperature dependencies, carried mobilities in the different impurity bands are obtained. The doping mechanism of In introduced in different proportions with vacancies is determined by impurity band state occupation in consecutive order according to their location on the energy scale and by the Fermi level position. The Fermi level is located in one of the impurity bands depending on proportion of In1+ and In3+ atoms and vacancies.