Surface Morphology and Composition of GaN Subjected to Photoelectrochemical Etching in KOH Aqueous Solution

抄録

n- and p-type GaN were photoelectrochemically etched in 1 M KOH under UV light illumination to investigate the relationship between photoelectrochemical etching properties, surface morphologies, and surface composition. The anodic dissolution of GaN was enhanced by UV light illumination. The surface morphology of GaN subjected to photoelectrochemical etching strongly depended on the type of doping. After photoelectrochemical etching, crystallographic orientated inhomogeneous structure formed on the n-GaN, and several pits formed on the p-GaN surface. Cathodic current was only observed in the p-GaN, and the current was caused by the reduction of oxygen or protons. Apparent changes of surface composition were not observed between GaN as received or subjected to photoelectrochemical etching. The XPS spectra suggested that the surface concentration of oxide formed on n-GaN subjected to photoelectrochemical etching was identical to the as received n-GaN.