A comparative study of the stability of Ga- and N-polar GaN films was made in different gas ambients (N-2, H-2, NH3, HCl). The Ga-polar films were observed to undergo a dissociative sublimation, while the N-polar films formed condensed Ga in addition to the gaseous species. The difference in polarity affects the morphology and bonding on the surface, and thus, stability of the atoms bonded to the surface. (C) NO4 Elsevier B.V. All rights reserved.