Influence of oxygen on the activation of <i>p</i>-type GaN

The presence of oxygen in the annealing environment can exhibit a strong influence on the activation of p-GaN, as demonstrated by experiments described in this letter. We activated p-GaN at 600–900 °C in four environments: ultrahigh purity (UHP) N2 gettered to remove residual O2, UHP N2 without gettering, 99.5% UHP N2/0.5% UHP O2, and 90% UHP N2/10% UHP O2. The resistivity of the p-GaN was lowest when O2 was intentionally introduced during activation and was highest when extra care was taken to getter residual O2 from the annealing gas. The experiments also demonstrate that unintentionally incorporated O2 can be at high enough levels to influence the activation process.