Atomic layer etching of GaN and AlGaN using directional plasma-enhanced approach

The directional atomic layer etching (ALE) of GaN and AlGaN has been developed. The GaN ALE process consists of cyclic Cl-2 plasma chemisorption and Ar ion removal. The etch per cycle (EPC) was 0.4 nm within the self-limiting regime, which is 50 to 100 V. The root-mean-square surface roughness R-RMS was 0.6 nm, which was improved from an initial roughness of 0.8 nm. For AlGaN ALE, BCl3 was added to the chlorine step to obtain a smooth surface with R-RMS of 0.3 nm and stoichiometry similar to the initial sample. The ultra smooth surface obtained by etching is promising for use in next-generation power devices. (C) 2017 The Japan Society of Applied Physics