POINT-DEFECTS IN THE MIXED CHALCOGENIDES BI(2)TE(3-X)X(X)(X=S, SE)

From the dependences of electrical conductivity sigma perpendicular to, and the Hall constant R(H)(($) over bar B parallel to ($) over bar c) of Bi2Te3-xSx crystals upon the value of x it is found that a transition from hole-like to electron-like conductivity takes place at x less than or equal to 0.12. The decrease in the hole concentration with increasing x is explained by the idea that an increasing content of incorporated S atoms in the anion sublattice gives rise to an increase in the anion vacancy concentration (V-A) and simultaneously the antisite defect concentration increases slightly as well. This model is not in contradiction with van Vechten's theory of the formation of vacancies in a crystal lattice. The results obtained for the system of Bi2Te3-xSx are compared with those for the system Bi2Te3-xSex.