Electronic structure of defects and impurities in III-V nitrides: Vacancies in cubic boron nitride.

Abstract

The electronic structures of boron and nitrogen vacancies in cubic boron nitride (BN) are investigated using the full-potential linearized augmented-plane-wave, full-potential linear-muffin-tin-orbital, and linear-muffin-tin-orbital--tight-binding approaches. All the methods give quantitatively consistent results on ideal cubic BN that are also compared with previous calculations. Using a 64-atom supercell, we have examined the electronic states of boron and nitrogen vacancies. Lattice relaxation around the vacancies is not considered. Both boron and nitrogen defect states appear to form well-defined narrow bands in the forbidden gap of c-BN. The ones for boron vacancy are located near the top of the valence band and are partially occupied. They represent ``acceptor levels of boron vacancy.'' For the nitrogen defect, the ``vacancy levels'' overlap with the states at the conduction-band edge. The characteristics of vacancy states, their localization degrees and influence on the electronic density of states, and charge distribution in c-BN crystals are discussed. These results suggest that both boron and nitrogen vacancies can be ``p-type'' and ``n-type'' doping agents, respectively, when the composition of c-BN deviates from ideal stoichiometry. \textcopyright{} 1996 The American Physical Society.