Enhanced performance of etched p-GaN p−i−n diodes via Mg diffusion-enabled Ohmic contacts

This work demonstrates a high-performance vertical GaN p−i−n diode based on a buried p-layer n-p−i−n epitaxial structure. The post-etch magnesium (Mg) diffusion process is applied to suppress the etch-induced surface damage on the p-GaN layer. The Mg diffusion effectively reduces the valence band barrier from 2 to 1.1 eV, yielding a low specific contact resistivity of 6.521 × 10 −4 Ω·cm 2 . As a result, the fabricated devices exhibit markedly enhanced forward characteristics, including a reduced turn-on voltage of 3.3 V and a specific on-resistance of 0.92 mΩ·cm 2 . Temperature-dependent forward I−V measurements indicate that the dominant carrier transport mechanism evolves from defect-related tunneling in the etched devices toward transport dominated by intrinsic p–n junction conduction after Mg diffusion. In addition, the devices exhibit excellent stability in forward conduction, with a voltage variation of approximately 0.028 V. These results indicate that Mg diffusion effectively improves the contact characteristics degraded by ICP etching and provide a viable approach for achieving high-performance and reliable vertical GaN power devices.