First-principles calculations were made of the stability and electronic structures of self-interstitials and vacancies in the hexagonal and cubic phases. It was found that the self-interstitials, Ni and Bi, in the hexagonal phase had low formation energies which were comparable to those of the vacancies, VN and VB. It was found that Ni was the most stable defect in the hexagonal phase, under N-rich and p-type conditions, followed by the N vacancy. This was consistent with the experimental observation of high concentrations of N interstitials and vacancies, and with the trapping of N in the hexagonal phase of thin films which had been grown by using ion-bombardment assisted deposition techniques. In the case of the cubic phase, the self-interstitials had high formation energies as compared with those of vacancies. As a result, the formation of vacancy-interstitial pairs in kick-out processes typically required much more energy in the cubic phase than in the hexagonal phase. It was suggested that a possible role played by ion bombardment, in favouring the growth of cubic films, was to generate a much higher number of defects in the hexagonal phase than in the cubic phase.

Stability of Native Defects in Hexagonal and Cubic Boron Nitride. W.Orellana, H.Chacham: Physical Review B, 2001, 63[12], 125205 (7pp)