The effect of annealing on structural, electrical, and optical properties of Ga-doped ZnO (GZO) films prepared by RF magnetron sputtering was investigated in air and nitrogen. GZO films are polycrystalline with a preferred 002 orientation. The resistivities of annealed films are larger than the as-deposited. The transmittance in the near IR region increases greatly and the optical band gap decreases after annealing. The photoluminescence spectra is composed of a near band edge emission and several deep level emissions (DLE) which are dominated by a blue emission. After annealing, these DLEs are enhanced evidently. (C) 2011 Elsevier B.V. All rights reserved.