ELECTRONIC-STRUCTURE OF DEFECTS AND IMPURITIES IN III-V NITRIDES - VACANCIES IN CUBIC BORON-NITRIDE

The electronic structures of boron and nitrogen vacancies in cubic bor on nitride (BN) are investigated using the full-potential linearized a ugmented-plane-wave, full-potential linear-muffin-tin-orbital, and lin ear-muffin-tin-orbital-tight-binding approaches. All the methods give quantitatively consistent results on ideal cubic BN that are also comp ared with previous calculations. Using a 64-atom supercell, we have ex amined the electronic states of boron and nitrogen vacancies. Lattice relaxation around the vacancies is not considered. Both boron and nitr ogen defect states appear to form well-defined narrow bands in the for bidden gap of c-BN. The ones for boron vacancy are located near the to p of the valence band and are partially occupied. They represent ''acc eptor levels of boron vacancy.'' For the nitrogen defect, the ''vacanc y levels'' overlap with the states at the conduction-band edge. The ch aracteristics of vacancy states, their localization degrees and influe nce on the electronic density of states, and charge distribution in c- BN crystals are discussed. These results suggest that both boron and n itrogen vacancies can be ''p-type'' and ''n-type'' doping agents, resp ectively, when the composition of c-BN deviates from ideal stoichiomet ry.