Dependence of transition-metal impurity levels on host composition in III-V semiconductors.

Abstract

Model calculations of substitutional transition-metal impurities in III-V semiconductors have been performed with the purpose of investigating how the defect energy levels vary as the host composition is changed. The calculations are based on the theory of Haldane and Anderson and include electron-electron interactions in a self-consistent manner. The band structure has been described in terms of an ${\mathrm{sp}}^{3}$ second-nearest-neighbor tight-binding approximation. We find that the transition-metal acceptor energy levels have fixed positions relative to the average vacancy level or the vacuum level independent of the chemical composition of the host material. This stability is a consequence of self-consistent competition between the strongly localized Coulomb interaction at the impurity site and the hybridization with the nearest neighbors.