Absolute surface energies of oxygen-adsorbed GaN surfaces

Absolute surface energies of reconstructed polar, nonpolar, and semi-polar GaN surfaces formed under oxide vapor phase epitaxy (OVPE) growth conditions were investigated via first-principles calculations. The relationships of stable surface orientations and surface structures with the growth conditions of Ga pressure and temperature were examined in terms of absolute surface energies. The stability of the surface orientation was in the order (0 0 0 1 ¯ ), (1 1 ¯ 0 1), (1 1 ¯ 0 0), (1 1 2 ¯ 0), (0 0 0 1), and (1 1 ¯ 0 1 ¯ ). High O concentrations on OVPE-grown GaN could be explained in relation to the stability of the (1 1 ¯ 0 1) surface. The stable (1 1 ¯ 0 1) surface consisted of N vacancies and H and O adatoms. Therefore, it was deduced that its appearance results in increased O impurity incorporation.