Charge-state calculations, based upon density-functional theory, were used to study the formation energy of H in wurtzite and zincblende phases as a function of the Fermi level. A comparison of the results revealed important differences, including a 0.56eV lower formation energy for H2 in wurtzite, and for various configurations of H2 and H in the 2 crystal structures. Moreover, H+ was found to be equally stable at bond-centred and anti-bonding sites in wurtzite, whereas it was unstable at bond-centred sites in zincblende. The N-H+ stretching-mode vibration frequencies, the clustering of H+ in p-type material and barriers to H diffusion were investigated in the wurtzite phase. A diffusion barrier of 1.6eV was found for H- in wurtzite GaN, and it was noted that there was a tendency to H+ clustering in p-type material.

Influence of Crystal Structure on the Lattice Sites and Formation Energies of Hydrogen in Wurtzite and Zinc-Blende GaN A.F.Wright: Physical Review B, 1999, 60[8], R5101-4