We have prepared the gallium oxide (Ga2O3) thin films on sapphire substrates by the metal organic chemical vapor deposition (MOCVD) technique. We have compared the two films with and without the thermal annealing by using the X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and the photoluminescence (PL) spectra. Postdeposition annealing of amorphous Ga2O3 films was found to increase the degree of crystallization and the surface roughness. The PL emission intensities of bands in the blue-green and the ultraviolet regions increased by the thermal annealing. (C) 2004 Elsevier B.V. All rights reserved.