Hydrogenation and Annealing Effects on Deep Levels in Unintentionally Doped n-Type GaN Epilayers Grown on Sapphire Substrates

Behaviors of deep levels in as-grown, hydrogenated, and hydrogenated and annealed GaN epilayers were investigated using thermally stimulated current (TSC) measurements. The TSC intensity, which corresponded to the trap concentrations of the deep levels for the hydrogenated GaN epilayer, decreased significantly in comparison with that for the as-grown sample. The TSC intensity, which was related to the trap concentrations of the hydrogenated GaN epilayer annealed at 600°C, did not change significantly in comparison with that for the sample which was hydrogenated only. These results can help improve understanding of the potential applications of hydrogenated and annealed GaN epilayers in optoelectronic devices in the blue region of the spectrum.