Molecular dynamics simulation of atomic layer etching for sidewall damage recovery in GaN-based structures.

Today, as GaN-based devices are becoming increasingly smaller, dry etching has been employed, but it has caused damage, particularly in InGaN/GaN multiple quantum well (MQW) structures exposed to Cl2-based reactive ion etching (RIE). Attempts to remove this damage with wet etching have had limitations. Therefore, atomic layer etching (ALE) has emerged as a promising technique to overcome the sidewall damage issues in GaN-based devices. This study utilized molecular dynamics (MD) simulations to investigate the optimal ALE process conditions for recovering plasma-induced damage at the atomic scale. The simulations systematically analyzed the effect of the Ar⁺ ion incidence angle on etching behavior and recovery efficiency. Three surfaces with initial damage conditions high, middle, and low were generated and then subjected to the ALE process. As a result, the ALE process was found to effectively remove both surface and subsurface amorphized regions, with more than ~47% reduction in damaged atoms observed across all damage levels, and ultimately converging to a comparable level of residual surface damage. Furthermore, a dual-angle approach using 60°~70° for deep damage removal followed by 80° for surface smoothing was identified as the most effective strategy for maximizing recovery while minimizing roughness. These findings highlight the strong potential of ALE to fundamentally recover MQW sidewall damage regardless of the initial damage level, while also providing critical physical insights and practical guidelines for optimizing the manufacturing processes of next-generation vertical GaN-based devices.