Epitaxial growth of GaN(0 0 0 1) is possible even using molecular beam epitaxy (MBE). Under the N-rich condition, nitrogen adatom on GaN(0 0 0 1) truncated surface adsorbed at an abnormal site, H3-site which is not the original site for wurtzite structure nor zincblende structure. The nitrogen at the H3-site is very stable and inactive so that the epitaxial growth is prevented. The first-principles calculation shows us that the Ga-rich condition is very helpful to assist epitaxial growth of GaN(0 0 0 1). (C) 2003 Elsevier Science B.V. All rights reserved.