We grew thick Ga1-xInxN epitaxial films on GaN templates having different crystal orientations. Reciprocal space mapping of asymmetrical X-ray diffraction showed that 1.1-mu m-thick Ga0.95In0.05N could be coherently grown on m-plane GaN, while those grown on a-plane and c-plane GaN showed partial relaxation. A 700-nm-thick Ga0.95In0.05N film with a threading dislocation density of approximately 1 x 10(8) cm(-2) can be successfully grown on a GaN template using a grooved underlying layer. The mechanism of strain relaxation in c-, a- and m-plane Ga1-xInxN films is discussed. (C) 2008 Elsevier B.V. All rights reserved.