Suppression of antistructural defects in crystals by an increased polarization of bonds

Single crystals of Sb2-xInxTe3 (x = 0·0−0·4), Bi2-xInxTe3 (x = 0·0−0·4) and Bi2Te3-x (x = 0·0−0·1) prepared using a modified Bridgman method have had their lattice parameters, electrical conductivity and Hall coefficient determined. The concentration of free current carriers (holes), as calculated from the Hall coefficient, in Sb2-xInxTe3 and Bi2-xInxTe3 crystals has been found to decrease with increasing In content, while in Bi2Te3-xSx crystals the concentration decreases with increasing S content. The observed effect is explained in terms of an increase in polarization of bonds caused by the substitition of In atoms for Sb or Bi atoms and S atoms for Te atoms, respectively. The increased polarity of the bonds InSb x(+δ)-Te and Bi-STe x(−δ) relative to the bonds Sb-Te and Bi-Te, respectively, suppresses the formation of antistructural defects in the studied crystals. The incorporation of In atoms into the Sb2Te3 or Bi2Te3 crystal lattice results in a decrease of hole mobility, whereas in Bi2Te3-xSx crystals this effect has not been observed.