Theoretical studies of defect states in GaTe

Abstract

Using first principle electronic structure calculations within density functional theory andthe supercell model, we have investigated the nature and formation energies ofdefect states associated with Ga and Te vacancies and Ge and Sn substitutionalimpurities in GaTe. We have also calculated the band structure of pure GaTe forcomparison with systems with defects and also to find out the importance of spin–orbitinteraction (SOI) on its band structure. We find that the top valence band at theΓ-point shifts up inenergy by ∼0.1 eV dueto the mixing of Te px–py and pz bands, this splitting being considerably smaller than in atoms where it is∼0.8 eV. From an analysis of charge densities and band structures associated with thedefect states, we find that most of them are strongly localized and lie deep in theband gap region. The calculated binding energy of the deep defect state and theε(−1/−2) transition level associated with the Ga vacancy appears to be in goodagreement with experiment. Formation energy calculations suggest thatVGa is the preferred intrinsic defect in GaTe.