ZnO thin film was deposited on semi-insulating GaAs by metal organic chemical vapor deposition (MOCVD). In situ annealing treatments were carried out under different temperature. Hall and photoluminescence (PL) measurements showed that the electrical and optical properties of ZnO film were sensitively dependent on annealing temperature. The as-deposited ZnO film showed n-type conductivity and intense near band edge ( NBE) emission combined with rather weak deep level (DL) emission. After annealing in the temperature of 520 and 560 degrees C the films exhibit p-type conductivity, meanwhile secondary ion mass spectroscopy demonstrated arsenic ion was uniformly distributed in the ZnO films. Distinctly recombination of donor acceptor pair (DAP) was observed from the p-type ZnO film. The calculated arsenic related acceptor binding energy is nearly consistent with that of As-Zn-2V(Zn) acceptor complex. When the annealing temperature up to 640 degrees C, Ga ion began to diffuse into ZnO film and the film returned to n-type as well as donor related emission reappeared in the spectrum. The influence of GaAs substrate on the electrical properties of ZnO films was also discussed. (C) 2008 Elsevier B. V. All rights reserved.