First-principles calculations were presented for the substitutional C impurity on the N and Ga sites, and substitutional and split-interstitial di-carbon pairs (2C) in cubic GaN. The pseudopotential approach and a plane-wave expansion were applied in the framework of density functional theory and local density approximation. The stability of C-based defects versus the Fermi level and preparation conditions was analyzed. Calculations taking into account several impurities and native defects in their charge states were performed in order to determine the defect which was formed at the highest concentration. The results provided information about consequences of C doping in cubic GaN. They were used to elucidate the compensation mechanism seemingly observed with the increment of the high C concentrations in recent experiments.

Carbon-Based Defects in GaN - Doping Behaviour. L.E.Ramos, J.Furthmüller, J.R.Leite, L.M.R.Scolfaro, F.Bechstedt: Physica Status Solidi B, 2002, 234[3], 864-7