FIRST PRINCIPLES STUDIES OF POINT-DEFECTS AND IMPURITIES IN CUBIC BORON-NITRIDE

The full-potential linear augmented-plane-wave (FLAPW) method within t he frameworks of the local density approximation and the large unit ce ll approach was used to carry out self-consistent calculations of vaca ncies, substitutional and interstitial Be impurity in cubic boron nitr ide (c-BN). It has been found that the Be substitutional impurity repl acing B leads to a shallow acceptor level just above the top of the va lence band. This result makes Be a typical p-type dopant in c-BN. Be r eplacing N leads to occupied and empty energy levels at the middle gap region, indicating an amphoteric character for this center. Be at tet rahedral interstitial sites induce deep levels at the upper part of th e band gap comprising two electrons and four holes for each center. Th e role played by these findings on the interpretation of experimental data taken on Be-doped c-BN is discussed. (C) 1998 Elsevier Science S. A. All rights reserved.