Characterization of a selective AlN wet etchant

The effects of a selective AlN wet etchant, AZ400K, on the morphology and chemical composition of capped and uncapped GaN surfaces were investigated. After etching an uncapped GaN thin film at 80 °C for 8 h, the surface morphology was unchanged. After an annealing pulse of 1500 °C was applied, AlN-encapsulated GaN surfaces exhibited morphology change due to surface rearrangement. No reaction occurred between the GaN and AlN, preventing the complete removal of AlN. AZ400K was found to completely etch AlN without damaging the underlying GaN film, thus enabling plasma-free processing of power and optoelectronic devices.