First principles studies of point defects and impurities in cubic boron nitride

The full-potential linear augmented-plane-wave (FLAPW) method within the frameworks of the local density approximation and the large unit cell approach was used to carry out self-consistent calculations of vacancies, substitutional and interstitial Be impurity in cubic boron nitride (c-BN). It has been found that the Be substitutional impurity replacing B leads to a shallow acceptor level just above the top of the valence band. This result makes Be a typical p-type dopant in c-BN. Be replacing N leads to occupied and empty energy levels at the middle gap region, indicating an amphoteric character for this center. Be at tetrahedral interstitial sites induce deep levels at the upper part of the band gap comprising two electrons and four holes for each center. The role played by these findings on the interpretation of experimental data taken on Be-doped c-BN is discussed.