Table 2.

Summary of optimal ALE process conditions as a function of ion incidence angle. The table compares damage recovery efficiency, surface roughness, etch depth behavior, and the recommended usage in multi-step atomic layer etching strategies for GaN-based MQW structures.

Ion incidence angle (°)	Damage recovery efficiency	Surface roughness	Etch depth control	Recommended usage
60°	High (rapid damage removal)	Higher (rougher surface)	Deeper material removal	Initial cycles for bulk damage removal
70°	Moderate	Balanced	Moderate control	Intermediate phase in ALE
80°	Slower recovery	Lowest (smoothest surface)	Shallow, precise etching	Final phase for surface refinement