The effect of thermal annealing on the electrical properties of highly transparent conductive Ga-doped ZnO (GZO) films deposited on glass substrates at 200 degrees C by an ion-plating deposition was investigated. GZO films were annealed in the temperature range from 200 to 600 degrees C for 30 min under the atmospheric pressure of high-purity N(2) gas. Up to 300 degrees C, GZO films were electrically very stable, and there was little change in resistivity. When the annealing temperature exceeded 400 degrees C, resistivity increased rapidly, originating from an abrupt decrease in carrier concentration. It was suggested to be due to both desorption of Zn from GZO films and grain boundary segregation of Ga clopants. (C) 2008 Elsevier B.V. All rights reserved.