Electrical properties of electrochemically energized n-GaN under reverse-bias conditions

Electrochemical energization of n-GaN was conducted under reverse-bias conditions as well as forward-bias conditions that were used in our previous studies for anodization, and electrical properties of energized n-GaN were examined. The surface composition and electrical properties of the energized n-GaN were evaluated by x-ray photoelectron spectroscopy (XPS) and temperature-dependent Hall-effect measurements, respectively. XPS analysis revealed that surface oxidation occurred even under reverse-bias conditions. Furthermore, while the electron concentration slightly increased under forward-bias conditions, it decreased by four to five orders of magnitude under reverse-bias conditions, suggesting significant electron trapping. These results clearly indicate that the effects of electrochemical energization on n-GaN differ significantly between forward- and reverse-bias conditions. Based on these findings, a surface conceptual illustration of n-GaN that explains these results is proposed.