The effect of electric fields upon the surface migration of Ga and N adatoms was studied during GaN growth via molecular beam epitaxy. When a direct current was used to heat the sample, long-distance migration of Ga adatoms and a diffusional asymmetry of N adatoms at steps were observed. If an alternating current was used, no such preferential adatom migration was found. This was attributed to the effective positive charges on surface adatoms. One implication of such current-induced surface migration, for GaN epitaxy, was that it would change the distribution of Ga adatoms at a growing surface. This was expected to make growth Ga-limited at one side of the sample, but N-limited at the other side. This would, in turn, lead to differing morphologies of the surface.

Current-Induced Migration of Surface Adatoms During GaN Growth by Molecular Beam Epitaxy. L.X.Zheng, M.H.Xie, S.J.Xu, S.H.Cheung, S.Y.Tong: Journal of Crystal Growth, 2001, 227-228, 376-80