Defect formation energies and homogeneity ranges of rock salt-, pyrite-, chalcopyrite- and molybdenite-type compound semiconductors

Employing the generalisation of Van Vechten's cavity model, formation energies of neutral point defects in pyrites (FeS2, RuS2), chalcopyrites (II-IV-V-2 and I-III-VI2) as well as molybdenites (MoS2, WS2) have been estimated. As input parameters the fundamental band gaps, work functions, electron affinities, surface energies, coordination numbers, covalent or ionic radii and unit cell parameters were used. The values calculated for tetrahedrally and octahedrally coordinated compounds agreed well with measured values. The data obtained can be used to calculate point defect concentrations and homogeneity ranges as a function of partial pressure and temperature. Introducing charged vacancies, the conductivity type can be predicted. (C) 2004 Elsevier B.V. All rights reserved.