Etching of AIGaN/GaN HEMT structures by Cl<inf>2</inf>-based ICP

AIGaN/GaN mesa etching using different plasma combinations of Cl2/Ar, Cl2/BCl3and Cl2/CF4by inductively coupled plasma was investigated. It was observed that the etch rate of Cl2/Ar increases linearly with the Ar content. In contrast to the Ar-based mixtures, Cl2/BCl3and Cl2/CF4plasma combinations show a damage-free surface. Furthermore, the lowest isolation current values achieved in devices with reduced sheet resistance were achieved by using Cl2/BCl3plasma.