Enhanced Low-Damage Quantitative Hybrid Cyclic Etching for AlGaN/GaN Heteroepitaxy: Process Optimization and Device Performance Improvement

The etching process is pivotal in the fabrication of GaN-based devices, directly influencing their performance. This study presents an enhanced low-damage hybrid cyclic etching technology for AlGaN/GaN heteroepitaxy structures, combining oxygen plasma oxidation with HCl etching to achieve atomic-scale precision. By carefully controlling the oxidation layer thickness, this method preserves a low surface roughness of 0.228 nm and achieves an etching rate of 0.45 nm/cycle with excellent consistency. Compared to conventional ICP dry etching and KOH wet etching evaluated under identical experimental conditions, the proposed technique significantly reduces etching-induced-damage. When applied to the ohmic contact formation of AlGaN/GaN HEMTs using the same metallization scheme and annealing process, devices fabricated with the new hybrid etching method demonstrated a significantly lower contact resistance of 0.76 Ω mm compared to those using conventional ICP etching ( 1.21 Ω mm) or no additional etching after SiN removal ( 1.37 Ω mm). Furthermore, these devices exhibited a threshold voltage of –6.5 V, a saturation drain current density of 880.55 mA/mm, and a knee voltage of approximately 4 V. This method also demonstrates potential for recessed gate etching and post-dry-etching damage repair, offering a promising solution for low-roughness surfaces processing with broad application prospects.