【Domestic Papers】3.0 kV β-Ga₂O₃-Based Vertical p-n Heterojunction Diodes With Helium- Implanted Edge Termination

      Researchers from the South China Normal University,  Nanjing University and Shenzhen University have published a dissertation titled "3.0 kV β-Ga₂O₃-Based Vertical p-n Heterojunction Diodes With Helium- Implanted Edge Termination" in IEEE Transactions on Electron Devices.

Project Support

      This work was supported in part by the National Key Research and Development Program of China under Grant 2024YFE0205100, in part by Guangdong Major Project of Basic and Applied Basic Research under Grant 2023B0303000012, in part by Guangdong Science Foundation for Distinguished Young Scholars under Grant 2022B1515020073, in part by Shenzhen Science and Technology Program under Grant KJZD20240903102738050, and in part by the Scientific Instrument Developing Project of Shenzhen University under Grant 2024YQ003.

      The authors would like to thank Sino Nitride Semiconductor Company Ltd. for device fabrication process and valuable discussion of the work.

Background

      Gallium oxide in beta phase (β-Ga₂O₃) is considered a promising candidate for high-voltage, high-frequency, and high-power applications due to its excellent material properties, such as an ultra-wideband gap of 4.9 eV, high theoretical field strength (8 MV/cm), and a Baliga’s figure of merit (FOM), FOM = V²_BR/R_on,sp ) superior to Si, SiC, and GaN materials. Unipolar power devices, specifically β-Ga₂O₃ Schottky barrier diodes (SBDs), have been demonstrated in recent years. Various termination techniques for suppressing crowded electric field at the device edges have been attempted to achieve high breakdown voltages (V_BR) and high FOM, such as trench structure, field plate structure, and Mg-ion implanted edge termination (ET). Although the great progress in unipolar devices has been made, bipolar p-n diodes can deliver higher V_BR and higher current capacity, owing to excellent current capability and higher reliability.

Abstract

      We demonstrated the vertical NiO/β-Ga₂O₃ p-n heterojunction diodes (HJDs) with a high breakdown voltage (V_BR) of 3000 V and a low on-resistance (R_{on, sp}) of 3.12 mΩ⋅ cm², resulting in a Baliga’s figure of merit (FOM) of 2.88 GW/cm². Specifically, an efficient and low-damage edge termination (ET) formed by the implantation of lightweight Helium atoms was introduced to inhibit the high electric field at the p-n junction of HJDs, thereby increasing V_BR of devices from 1330 to 3000 V. The reverse leakage mechanisms were fit and analyzed, revealing distinct breakdown mechanisms in He-implanted devices. The simulation results confirmed the peak electric field at the p-n junction of devices can be effectively suppressed by He-implanted ET. Meanwhile, a narrow change of devices’R_{on, sp} occurred after He implantation and the low-R_{on, sp} forward conduction of devices was confirmed by efficient charge transfer of heterojunction with density functional theory (DFT) calculation. This work may provide a new insight into the design and fabrication of high-power, low-loss β-Ga₂O₃ bipolar power devices.

Conclusion

      By employing lightweight Helium atoms for implantation as an efficient and low-damage ET, the electric field at the p-n junction of devices is effectively suppressed. We fabricated vertical Ga₂O₃ HJDs with a high V_BR of 3000 V and a low R_{on, sp} of 3.12 m·cm², yielding a FOM of 2.88 GW/cm². This research could offer valuable new perspectives on the design and manufacturing of high-power, low-loss β-Ga₂O₃ bipolar power devices.