Using first-principles electronic structure calculations within density functional theory and the super-cell model, an investigation was made of the nature and formation-energies of defect states associated with Ga and Te vacancies and Ge and Sn substitutional impurities in GaTe. The band structure of pure GaTe was also calculated for comparison with systems with defects to determine the importance of spin-orbit interaction to its band structure. It was found that the top valence band at the Γ-point shifted up in energy by ~0.1eV due to the mixing of Te px–py and pz bands. This splitting was considerably smaller than in atoms, where it was ~0.8eV. From an analysis of the charge densities and band structures associated with the defect states, it was found that most of them were strongly localized and lay deep within the band-gap region.

Theoretical Studies of Defect States in GaTe. Z.Rak, S.D.Mahanti, K.C.Mandal, N.C.Fernelius: Journal of Physics - Condensed Matter, 2009, 21[1], 015504