We investigated the structural, electrical, and optical properties of ZnO thin films grown at different VI/II ratios on sapphire substrates by metalorganic chemical vapor deposition Transmission electron microscopy and X-ray diffraction revealed the epitaxial nature with a reduced dislocation density of the ZnO films grown at increased VI/II ratios The carrier concentration of the films increased to 4 9 x 10(18) cm(-3) and their resistivity decreased to 1 4 x 10(-1)Omega cm at a VI/II ratio of 513 4 mu mol/min The ZnO films also showed good optical transmittance (>80%) in the visible and near-infrared wavelength regions. The room temperature PL revealed a strong band-edge emission with a weak deep level emission, suggesting the good crystalline quality of the ZnO films on the sapphire substrates Furthermore, the intensity ratio of the band-edge emission to the deep-level emission (I(UV)/I(Vis)) increased with increasing VI/II ratio (C) 2009 Elsevier B V All rights reserved