A c-oriented GaN film was grown on a r-plane sapphire substrate by utilizing hydride vapor phase epitaxy. This non-typical orientational relation between the film and the substrate was possible by spontaneous transition in preferred orientation, and voids were spontaneously formed in an orientation-transition layer. This c-oriented thick GaN film was then self-separated from the substrate during cool-down process to room temperature after the growth. This intriguing phenomenon of the self-separation of crack- and strain-free GaN is attributed to the spontaneous formation of voids during the preferred orientation-transition, and suggests a novel method to fabricate crack-and strain-free GaN freestanding templates. (C) 2009 Elsevier B.V. All rights reserved.