Positive and negative effects of oxygen in thermal annealing of p-type GaN

The effect of oxygen on ambient gas on activating p-GaN by rapid thermal annealing was investigated. When the ratio of N₂ to O₂ is 4:1, the sample activated after annealing at 750 °C exhibits the best electrical properties with respect to resistivity. It is confirmed that the concentration of hydrogen which passivates Mg acceptors in GaN decreases more efficiently when oxygen is introduced into N₂ ambient gas. Although oxygen-involved annealing at higher temperature may further reduce the concentration of hydrogen, the resistivity of p-GaN may increase due to the negative effect caused by too much incorporation of oxygen-related donors.