An investigation was made of the nature of the defect states associated with substitutional impurities (Cd, In, Sn) and both Ga and Se vacancies in GaSe using ab initio electronic structure methods within density functional theory. These calculations were done using super-cell model allowing for internal atomic relaxation. Binding energies of defects obtained in this model were compared with effective mass approximation results. Significant central cell corrections were present for most of the defects. This was consistent with charge densities associated with the defect states that showed clearly their strongly localized nature. Because of the difficulties associated with LDA/GGA in giving the correct band gap in semiconductors, the acceptor binding energies were compared only with available experiments. The theoretical results agreed well with the experiment for CdGa and VGa.

Electronic Structure of Substitutional Defects and Vacancies in GaSe. Z.Rak, S.D.Mahanti, K.C.Mandal, N.C.Fernelius: Journal of Physics and Chemistry of Solids, 2009, 70[2], 344-55