First-principles calculations were made of the formation energy of H-terminated (10¯10) surfaces. The calculations indicated that H adsorption on this surface would proceed via the saturation of pairs of Ga and N dangling bonds, rather than via the exclusive occupation of only one type of bonding site. At absolute zero, the surface energy of the fully H-terminated surface was found to be 0.02eV/cell; as compared with 1.95eV/cell for the bare surface. Results were presented for the N-H and Ga-H stretching and bending eigen-frequencies. Dissociative adsorption of NH3 via the formation of N-H and Ga-NH2 bonds was exothermic, and reduced the surface formation energy to a value which was less than 0.1eV at absolute zero.

J.E.Northrup, R.Di Felice, J.Neugebauer: Physical Review B, 1997, 56[8], R4325-8