(BI0.5SB0.5)2TE3 CRYSTALS DOPED WITH INDIUM ATOMS

(Bi0.5Sb0.5)2Te3 single crystals doped with In atoms (c(In) = 0 to 9.8 x 10(20) cm-3) are prepared by the modified Bridgman method. From the analysis of the measurements of reflection spectra in the plasma resonance-frequency region, electrical conductivity, and the Seebeck coefficient it is found that an increase in the concentration of In atoms in the crystal lattice of (Bi0.5Sb0.5)2Te3 crystals results in a decrease in the hole concentration. This effect is explained by the formation of substitutional point defects of In(Bi)x or In(Sb)x which result in an increase in the bond polarity of the structural lattice. The higher ionicity of the chemical bonds in the mixed crystals leads to a decrease of the concentration of antisite defects of Bi(Te)' and Sb(Te)' with a simultaneous decrease of the free current carriers, i.e. holes.