Abstract 

  In this work, we demonstrate a novel doping process via self-aligned nitrogen (SA-N₂) plasma treatment of the NiO/β-Ga₂O₃ heterojunction diodes. The SA-N₂ plasma-treated heterojunction diodes exhibit improved breakdown voltage from 1080 V to 1731 V while maintaining a high on-off ratio (I_ON/I_OFF) exceeding 10¹¹ and achieving a reduced specific on-resistance (R_on.sp). It is found that the SA-N₂ plasma treatment forms a resistive region acting as a shallow guard ring in the β-Ga₂O₃ around the anode. It is also confirmed that doped N plays the role of both a shallow acceptor and a deep acceptor in NiO and β-Ga₂O₃, respectively. This process can be easily and cost-effectively applied to the heterojunction structure, contributing to further performance improvement of the wide bandgap power device.