Middle-frequency magnetron sputtering method was adopted to deposit GaN films on glass substrate without substrate heating. The X-ray diffraction intensity depends strongly on the total gas pressure. No diffraction pattern could be observed at total pressure below 0.5 Pa. On the other hand, total pressure above 1.0 Pa would also deteriorate the crystallization of the GaN films. Films produced under optimal conditions had an almost 1:1 N:Ga ratio as determined by energy dispersive X-ray spectroscopy. Temperature dependence photoluminescence was used to investigate the optical properties of GaN films and the origin of the emission peaks was discussed. Broadening of characteristic photoluminescence and Raman scattering was observed and attributed to growing strain. (C) 2008 Elsevier B.V. All rights reserved.