Atomic layer etching of AlGaN using Cl2 and Ar gas chemistry and UV damage evaluation

Abstract

The atomic layer etching (ALE) characteristics of AlGaN using Cl2 plasma in the modification step and Ar plasma in the removal step were investigated in comparison with conventional reactive ion etching (RIE). Although surface roughening and GaN composition changes were observed in the RIE process, the ALE process did not result in such changes. However, the etching damage of the AlGaN layer evaluated using cathodoluminescence in AlGaN/GaN stacked films in the case of ALE was 30% higher than that in RIE. This was attributed to the longer process time of ALE compared to RIE. The GaN layer underneath the AlGaN layer was also damaged. This could be mainly caused by UV photons during the modification step using Cl2 plasma. The authors introduced a modification step using Cl2 gas instead of Cl2 plasma; thus, the etching damage was successfully reduced while maintaining good surface characteristics.