Low-damage p-GaN Surface for Ohmic Contact after Passivation Layer Removal by Atomic Layer Etching

In this work, we present a low-damage p-GaN surface processed by atomic layer etching (ALE), enabling high-performance Ohmic contacts. The mechanism underlying surface modifications introduced by various etching processes were studied in detail. Compared to conventional dry etch, ALE preserves the pristine surface stoichiometry comparable to as-grown p-GaN, effectively suppressing the formation of detrimental surface defects. Crucially, this atomic-level controlled process minimizes the increase in downward band bending and maintains the intrinsic surface electrical properties. Thus, metal contacts fabricated on the ALE-processed p-GaN exhibit an excellent Ohmic behavior. Collectively, these results not only establish low-surface-degradation contacts, but also provide a fundamental understanding required for advancing GaN-based device physics and designs.