Time-dependent hydrogen annealing of Mg-doped GaN

Unintentional doping by hydrogen is a concern for industrial growth of p-type GaN which is important in creating blue LEDs and high frequency devices. Using electron paramagnetic resonance (EPR) we investigated hydrogen passivation in p-type nitrides. Samples included conventional GaN and Al$_{x}$Ga$_{1-x}$N(x=0.12,0.28) grown by chemical vapor deposition (CVD) with 1-4x10$^{19}$ cm$^{-3}$ Mg and GaN grown by Metal Modulation Epitaxy (MME) yielding 1.5x10$^{20}$ cm$^{-3}$ Mg. The Mg signal was observed during isothermal anneals in N$_{2}$:H$_{2}$ (92{\%}: 7{\%}). The Mg EPR signal unexpectedly increased below 600$^{\circ}$C in GaN, but no changes were observed in AlGaN. The MME Mg EPR signal began decreasing after 10 min at 400$^{\circ}$C, while the Mg intensity of AlGaN did not start reducing until 500$^{\circ}$C. As expected the Mg EPR signal in the CVD GaN quenched at 700$^{\circ}$C, as did the signal in AlGaN. However, the intensity of the Mg signal in MME samples was eliminated after only 20 min at 500$^{\circ}$C. The different temperature dependence suggests that hydrogen diffusion is affected by increased Mg concentration. These studies are integral for the advancement of p-type GaN.