One- and two-step rapid thermal annealing (RTA) for activating Mg-doped p-type GaN films had been performed to compare with conventional furnace annealing (CFA). The two-step annealing process consists of two annealing steps: the first step is performed at 750 degrees C for 1 min and the second step is performed at 600 degrees C for 5 min in pure O-2 or air ambient. It is found that the samples annealed in air ambient exhibit poor electrical properties as compared to those annealed in pure O-2. Compared to one-step RTA annealing and CFA annealing, the samples with two-step annealing exhibit higher hole concentration and lower resistivity. This means that the two-step annealing is a powerful method to enhance the electrical performance of Mg-doped p-type GaN films. Similar results were also evidenced by photoluminescence (PL) measurement. Possible mechanism was confirmed by secondary ion mass spectrometry analysis. (c) 2006 Elsevier B.V. All rights reserved.