Point Defects in Sb2Te3−xSexCrystals

Abstract

Improved ideas on point defects in the Sb2Te3−xSexcrystals are formulated in this paper. Measurements of the Hall coefficient for a series of Sb2Te3−xSex(x=0–1) crystals served to determine the concentration of holes as a function of the selenium content in the lattice of the mixed crystals. The obtained variations of the hole concentration, linked hitherto solely with the decrease in the concentration of antisite (AS) defects of the Sb′Tetype, are explained using a model describing the interaction of the Se atoms entering the lattice not only with AS defects but also with the vacancies in the tellurium sublattice. The original concentration of AS defects in undoped Sb2Te3crystals, approximately 11.3×1019, drops with increasingx, reaching for the Sb2Te2Se crystal a value of 3×1019cm−3; the concentration of vacancies in the anion sublattice drops slightly: from a value of 2.5×1019cm−3down to 0.7×1019cm−3. The calculated variations of the concentration of holes, AS defects, and V••Tevacancies are in agreement with the idea that the increase in the polarity of bonds gives rise to a decrease in the concentration of AS defects and in the concentration of anion vacancies.