Selective etching of GaN over AlGaN through low-damage AlGaN surface processing at high temperatures

In this study, low-damage selective etching of GaN over Al0.24Ga0.76N was achieved using O2-added Cl2 plasma at a high substrate temperature of 400 °C. Specifically, etching using 7% O2-added Cl2 plasma at a bias voltage of 57 V achieved an etching selectivity of 14. Etching inhibition on the AlGaN surface was evaluated using in situ x-ray photoelectron spectroscopy, which revealed that Ga–O–N bonds formed at high temperatures selectively halted etching, differing from the Al–O-bond-based inhibition observed at 25 °C. This high-temperature process mitigates plasma-induced damage, preserving the photoluminescence intensity of near-band-edge emissions in AlGaN.