Thin films of GaN were grown on template substrates of 4-mu m-thick GaN layers on sapphire substrates by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE) in a new-design reactor with the shape T. Wide range of growth temperature from 520 to 1100 degrees C was explored. At low temperature growth between 550 and 690 degrees C, dimethylhydrazine (DMHy) was used as source of atomic nitrogen while ammonia (NH3) was used at high temperature growth (1000-1100 degrees C). At low temperature micro-Raman spectroscopy revealed a significant relaxation of the selection rules for the scattering by the optical phonons in the films grown at lower temperatures. Variation H of the intensity ratio for E-2(H) and E-1 phonon modes has been attributed to changes in the structural quality of the films grown at different temperatures. At high temperature, the quality of GaN layers were comparable to that of the substrate before growth. (c) 2006 Elsevier B.V. All rights reserved.