The atomic and electronic structures of H-vacancy complexes were investigated by means of pseudopotential density-functional calculations. The calculated formation energies provided information as to the likelihood of incorporation of these complexes into n-type or p-type material. The predicted binding energies provided a measure of the dissociation energy. The estimated vibrational frequencies also yielded a signature, for the complex, that might facilitate experimental identification. It was suggested that an observed red-shift corresponded to a decrease in the intensity of the L1 line, accompanied by an increase in intensity of a new line that was related to the N vacancy. The as-grown material could contain a certain concentration of hydrogenated N vacancies which had a level, near to the conduction band, that was thought to give rise to the L1 line. When the material was annealed, the hydrogenated vacancy complexes dissociated. The calculated removal energy of 1.56eV was consistent with complex dissociation at around 500C. The resultant N vacancies had a level, near to the valence band, which was suggested to be responsible for a line at around 2.9eV (420nm). It was noted that the +/3+ transition of the N vacancy was associated with a very large lattice relaxation.

Interactions of Hydrogen with Native Defects in GaN. C.G.Van de Walle: Physical Review B, 1997, 56[16], R10020-3