Influence of oxygen on the activation of p-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) ${\mathrm{N}}_{\mathrm{2}}$ gettered to remove residual ${\mathrm{O}}_{\mathrm{2}},$ UHP ${\mathrm{N}}_{\mathrm{2}}$ without gettering, 99.5% UHP ${\mathrm{N}}_{\mathrm{2}}\text{/0.5\%}$ UHP ${\mathrm{O}}_{\mathrm{2}},$ and 90% UHP ${\mathrm{N}}_{\mathrm{2}}\text{/10\%}$ UHP ${\mathrm{O}}_{\mathrm{2}}.$ The resistivity of the p-GaN was lowest when ${\mathrm{O}}_{\mathrm{2}}$ was intentionally introduced during activation and was highest when extra care was taken to getter residual ${\mathrm{O}}_{\mathrm{2}}$ from the annealing gas. The experiments also demonstrate that unintentionally incorporated ${\mathrm{O}}_{\mathrm{2}}$ can be at high enough levels to influence the activation process.