"Carbon-based defects in GaN: doping behaviour",
L.E. Ramos, J. Furthmüller, J.R. Leite, L.M.R. Scolfaro, and F. Bechstedt,
phys. stat. sol. (b) 234 , 864 (2002).

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