A study was made of the mechanism of H passivation, in Mg-doped material, by means of  ab initio  calculations. It was found that Mg which substituted at Ga sites favored Td symmetry, and that the hydrogenation of Mg-doped material was energetically more stable than was that of Mg-free material. The 2 calculated local vibrational modes of Mg-H complexes agreed well with experimental data. Upon introducing H into Mg-doped material, a new photoluminescence line appeared in the gap and in the Mg-H complex, the H acquired a positive charge state and the Mg acceptor acquired a negative charge state. The electrostatic interaction between H and acceptor Mg, as well as strong N-H bonding, contributed to the high stability of the Mg-H complex in this material.

Y.Okamoto, M.Saito, A.Oshiyama: Materials Science Forum, 1995, 196-201, 981-6