Photoenhanced wet etching of gallium nitride in KOH-based solutions

Abstract

Photoelectrochemical etching (PEC) of n+-GaN in KOH and AZ400K photoresist developer is presented. We compare the two solutions used for PEC etching without an external bias. The influence of etchant concentration and of the intensity of ultraviolet illumination was studied with emphasis on the resulting etched surface quality. The quality of the shallow etched surface and its roughness are presented. The AZ400K etchant was applied to shallow etching of n+-GaN with threading dislocation densities in the range of 109–1010 cm−2. Moreover, the first analysis of photocurrent monitoring during the electrochemical etching of GaN epitaxial layers in KOH is presented. We found that photocurrent very sensitively reflected the changes in the quality of the etched surface.