Energetics of carbon and oxygen impurities and their interaction with vacancies in cubic boron nitride

We investigate, through first-principles calculations, the energetics of su bstitutional carbon and oxygen impurities as well as complexes involving th ese impurities and vacancies in cubic boron nitride (c-BN). The formation e nergies and the electronic and structural properties of these defects in th eir various charge states are investigated. We find that, under a boron-ric h condition, both the carbon and the oxygen impurities at the nitrogen site (C-N and O-N) have formation energies comparable to or lower than those ca lculated for the vacancies, which are the lowest-energy intrinsic defects. Regarding defect complexes, we find that the donor character observed for t he nitrogen vacancy (V-N) can be compensated by the C-N impurity in the for mation of a V-N-C-N complex which has low formation energies. We also find that the V-B-O-N complex has low formation energies under n-type conditions . In contrast to the above mentioned complexes, we find that the V-B-C-B co mplex has high formation energies under a boron-rich condition, and shall o nly occur under a nitrogen-rich condition.