Epitaxial thin films were grown by the low-energy N-ion beam-assisted deposition of Ga onto c-plane sapphire. By using X-ray diffraction and transmission electron microscopy, the influence of ion bombardment-induced defects upon the formation of unwanted cubic GaN in the hexagonal-GaN films was investigated. The results showed that, in all films containing the cubic polytypes, it appeared in twinned form. An increase in the ion energy as well as the ratio of N-ion flux to Ga-atom flux led to an increase in the amount of cubic polytype in the films.

Influence of Defects in Low-Energy Nitrogen Ion Beam Assisted Gallium Nitride Thin Film Deposition. J.W.Gerlach, S.Sienz, W.Attenberger, B.Rauschenbach: Physica B, 2001, 308-310, 81-4