[TuP3A] Epitaxy and process

[TuP3A-06] Investigation on Morphology Evolution of MOCVD Regrown n⁺-GaN for Ohmic Contacts in GaN-based HEMTs

〇Yuxi Zhou¹, Jiejie Zhu¹, Mingchen Zhang¹, Lingjie Qin¹, Mengdi Li¹, Bowen Zhang¹, Xiaohua Ma¹ (1. National Engineering Research Center of Wide Band-gap Semiconductor, Faculty of Integrated Circuit, Xidian University (China))

Ohmic contact resistance (R_c) is a critical bottleneck for GaN HEMTs. While MOCVD regrowth enables low R_c, controlling surface morphology remains challenging. Contrary to the assumption that plasma etching induces roughness, our AFM analysis reveals that optimized BCl₃/Cl₂ etching preserves smoothness, whereas high-temperature NH₃ pre-treatment is the dominant degradation source. Driven by mass transport to minimize surface energy, this step induces severe roughness (surging to 21.3 nm) in patterned regions, which is amplified during epitaxy. Furthermore, a critical trade-off is identified: while high-temperature growth (1065°C) improves morphology, it compromises advanced heterostructures, whereas lower temperatures trigger hexagonal defect proliferation. These findings highlight the urgent need for optimized low-temperature regrowth strategies.