Simple wet etching of GaN

We discuss investigations into a contactless UV-enhanced wet etching technique for GaN. The technique utilizes the oxidising agent potassium persulfate to consume photogenerated electrons, thus avoiding the need for an electrical contact to an external cathode. The etch rate is strongly dependent on illumination intensity and uniformity and on the pH of the KOH solution, as is the roughness of the etched surface. The implementation of a dual illumination scheme whereby an additional UVC lamp was used to illuminate only the solution and not the wafer, resulted in an increased etch rate and smoother etched surface. Finally, the ohmic nature of contacts deposited on n-type GaN that had been etched in this manner was found to be improved compared to contacts on the unetched surface.