The strain relaxation was investigated in InxGa1-xN films grown pseudomorphically on GaN buffer layer. The shift of dominant peaks originated from In0.035Ga0.965N films which were thinner than the critical thickness was observed with the increasing film thickness. Considering the same thermal strains in all the samples, this is attributed to the relaxation of the in-plane strains that resulted from the increased common in-plane lattice constant of coherently grown-In0.035Ga0.965N films with the increasing thickness. (C) 2002 Elsevier Science B.V. All rights reserved.