Formation of Thin Native Oxide Layer on n-GaN by Electrochemical Process in Mixed Solution with Glycol and Water

In this paper, we report on the feasibility of oxidizing n-GaN by an electrochemical process in a mixture containing an aqueous solution of tartaric acid and propylene glycol. Photons generated by UV illumination were supplied at the electrolyte-GaN interface during the oxidation process. In the constant-voltage mode, X-ray photoelectron spectroscopy analysis revealed that relatively thick Ga oxide layer formed on the n-GaN surface. However, the oxide surface was very rough. In addition, we found metallic Ga components in the oxide layer or at the oxide-GaN interface for longer oxidation times. On the other hand, a thin Ga 2 O 3 layer with a smooth surface was grown by a constant-current process.