Aluminum-doped zinc oxide (AZO) films were prepared using an electron-beam evaporation system to form Schottky contacts on n-type GaN at depositing temperatures varied from 100 to 400 degrees C. The current-voltage (I-V) measurements which showed a rectifying characteristic were carried out to deduce the Schottky barrier heights (SBHs) according to the thermionic emission theory. The SBHs were calculated by using a linear curve fit to forward characteristics of In(I) against V, and have a small alteration around 0.7 eV. Hall-effect measurements were carried out to illuminate the alteration of the SBHs that were mainly affected by the carrier concentration of the AZO films. It has been found that the SBH ascends as the carrier concentration decrease, and the dislocations play an important role on the leakage current of the contacts. (C) 2012 Elsevier B.V. All rights reserved.