An investigation was made of interactions between H and dopant impurities, in this material, by using first-principles calculations. The results revealed a fundamental difference in the behaviors of H in p-type and n-type samples. In particular, it was explained why the H concentrations in n-type material were low, and why H had a beneficial effect upon acceptor incorporation in p-type material. Overall, the conclusions supported the potential use of H as a means of improving the doping of wide-bandgap semiconductors, although the approach was not generally applicable. In order to be able to exploit H passivation as a method for enhancing doping, the H had to be the predominant compensating defect. That is, its formation energy had to be lower than that of all native defects, and be comparable to the formation energy of the dopant impurity. Also, the activation energy which was required to dissociate the H-impurity complex, and to remove or neutralize H, had to be lower than the activation energies for native defect formation and lower than the diffusion barrier of the impurity. Finally, the dissociated H atom had to be highly mobile.

J.Neugebauer, C.G.Van de Walle: Applied Physics Letters, 1996, 68[13], 1829-31