Doping in this material was considered on the basis of state-of-the-art first-principles calculations. In the case of n-type doping, it was found that N vacancies were too high in energy to be incorporated during growth and were not responsible for unintentional n-type conductivity, whereas Si and O could be incorporated in large numbers and were likely to cause unintentional n-type doping. The properties of O, including a propensity to DX-center formation, suggested that it was the main cause of unintentional n-type conductivity. The DX transition did not occur in zincblende material. The Ga vacancies were thought to be the likely source of yellow luminescence. In the case of p-type doping, it was found that the solubility of Mg was the main factor which limited the hole concentration. The incorporation of Mg at interstitial sites or antisites was not a problem. It was noted that H had a beneficial effect upon p-type doping because it suppressed compensation and enhanced acceptor incorporation. The compensation of acceptors by N vacancies could occur. No other acceptor impurity exhibited characteristics that were superior to those of Mg.

C.G.Van de Walle, C.Stampfl, J.Neugebauer: Journal of Crystal Growth, 1998, 189-190, 505-10