High-quality ZnO films were grown on epi-GaN predeposited on c-Al2O3 substrates using low-pressure metal-organic chemical vapor deposition (MOCVD). Detailed study of the X-ray diffraction spots and patterns by different diffractometers showed high structural perfection of the zinc oxide layer, which indicated that the growth of ZnO film was strongly c-oriented. The full-width at half-maximum (FWHM) of the omega-rocking curve was 0.39degrees. Surface morphology of the films studied by AFM showed that the growth of the ZnO film followed the regular hexagonal column structure with about 500 nm grain diameter. Zn and 0 elements in the deposited ZnO/GaN/Al2O3 films were investigated and compared by X-ray photoelectron spectroscopy (XPS), in which the dissociative 0 and Zn atom peak was hardly observed. The ratio of O/Zn atoms of the film was about I with O-rich. Photoluminescence spectra of the ZnO films grown, on epi-GaN showed dominating exciton emission peak, and the deep-level emission which was obvious on ZnO/Al2O3 film had hardly been observed. (C) 2003 Elsevier B.V. All rights reserved.