Mapping etching induced damages on GaN surfaces using scanning internal photoemission microscopy

In this study, we used scanning internal photoemission microscopy (SIPM) to investigate damage on the n-GaN surface, which were induced by inductive coupled plasma (ICP) etching in conjunction with a recovery process by annealing. We formed Pd Schottky electrodes on n-GaN surfaces including selectively ICP-etched regions, and conducted two-dimensional mapping of the photoyield (Y). With SIPM, we could clearly visualize the etched regions in the Y map, where Y increased 1.4 times and the Schottky barrier height (qϕB) decreased by 0.32 eV, as compared with unetched regions. Upon annealing at 700 °C and 800 °C, both Y and qϕB values recovered. When we increased the annealing temperature to 900 °C, Y decreased remarkably in the both etched and unetched regions, and the etching patterns in the Y maps disappeared. These results indicate that SIPM is effective for mapping etching damage and recovery processes with high sensitivity.