POINT-DEFECTS IN SB2TE3-XSEX CRYSTALS

Improved ideas on point defects in the Sb2Te3-xSex crystals are formul ated 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 m ixed crystals. The obtained variations of the hole concentration, link ed hitherto solely with the decrease in the concentration of antisite (AS) defects of the Sb'(Te) type, are explained using a model describi ng the interaction of the Se atoms entering the lattice not only with AS defects but also with the vacancies in the tellurium sublattice. Th e original concentration of AS defects in undoped Sb2Te3 crystals, app roximately 11.3 x 10(19), drops with increasing x, reaching for the Sb 2Te2Se crystal a value of 3 x 10(19) cm(-3); the concentration of vaca ncies in the anion sublattice drops slightly: from a value of 2.5 x 10 (19) cm(-3) down to 0.7 x 10(19) cm(-3). The calculated variations of the concentration of holes, AS defects, and V-Te(..) vacancies are in agreement with the idea that the increase in the polarity of bonds giv es rise to a decrease in the concentration of AS defects and in the co ncentration of anion vacancies. (C) 1997 Academic Press.