【Member Papers】3 kV-Class β-Ga₂O₃ Lateral MOSFETs With Superior High-Temperature Leakage Suppression Enabled by an Ozone-Grown Semi-Insulating Buffer Layer

      Researchers from the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences 、Harbin Institute of Technology and Hangzhou Garen Semiconductor Company Ltd have published a dissertation titled "3 kV-Class β-Ga₂O₃ Lateral MOSFETs With Superior High-Temperature Leakage Suppression Enabled by an Ozone-Grown Semi-Insulating Buffer Layer " in IEEE Transactions on Electron Devices.

Background

      With an ultra‑wide bandgap of 4.8 eV, excellent Baliga’s figure of merit, and commercially available melt‑grown bulk substrates, β‑Ga₂O₃ is a promising candidate for next‑generation power electronics outperforming SiC and GaN. In recent years, β‑Ga₂O₃‑based power devices have achieved great progress. Lateral MOSFETs have drawn much attention owing to their good reliability and breakdown performance.

      Nevertheless, high‑temperature leakage remains a critical challenge for lateral β‑Ga₂O₃ devices. At 200 °C, the OFF‑state leakage current commonly rises to 10⁻³ ~ 10⁻⁴ mA/mm. Conventional devices adopt Fe‑doped semi‑insulating substrates. Although Fe compensates free electrons at room temperature, compensated electrons get thermally activated at high temperature and produce substrate leakage paths. Moreover, donor‑type traps in unintentionally doped buffer layers and their interfaces bring additional lateral leakage. Previous works adopted Mg‑doped buffer layers or Fe ion‑implanted layers for leakage suppression. However, Mg and Fe dopants tend to diffuse during thermal fabrication processes, leading to degraded interfacial quality and poor device reliability. To address this issue, the team prepared intrinsic semi‑insulating buffer layers by pulsed laser deposition (PLD) under ozone ambient and investigated improvements on high‑temperature and high‑voltage electrical performance.

Abstract

      Ultra wide bandgap β-Ga₂O₃ holds great promise for next-generation high-voltage power electronics, yet its practical application is severely hampered by premature breakdown and excessive OFF-state leakage at elevated temperatures. Here, we address the critical challenge by introducing an O₃-assisted-grown semi-insulating buffer layer in lateral β-Ga₂O₃ MOSFETs. The buffer layer exhibits a high density of deep-level acceptor defects, specifically gallium vacancies and gallium-oxygen divacancy complexes, as revealed by photoluminescence spectroscopy, which effectively compensate thermally activated carriers and suppress leakage pathways. Devices incorporating this buffer layer achieve a record breakdown voltage exceeding 3 kV among pulsed laser deposition (PLD)-grown lateral β-Ga₂O₃ MOSFETs without a field plate, and a specific on-resistance of 206.84 mΩ·cm². Moreover, at an operating temperature of 200 °C, the OFF-state leakage current is reduced by nearly two orders of magnitude compared to devices without the buffer layer. Temperature-dependent current-voltage measurements and TCAD simulations reveal that the superior high-temperature insulation originates from the deep level defects (2.4–3.1 eV) in the O₃-grown buffer layer, which contrasts with the shallower Fe-related acceptor level (~0.8 eV) in conventional substrates. This work demonstrates that defect-engineered buffer layers offer a viable and scalable pathway to exceptional high-temperature stability in β-Ga₂O₃ lateral power devices.

Highlights

      The team adopted PLD to grow semi‑insulating β‑Ga₂O₃ buffer layer under ozone ambient. High‑density deep‑level acceptor defects including gallium vacancies and gallium‑oxygen divacancy complexes are introduced without extrinsic doping or ion implantation, avoiding performance degradation induced by dopant diffusion under high‑temperature process.

      Compared with devices without buffer layer, the MOSFET equipped with ozone‑grown buffer layer achieves nearly two‑orders‑of‑magnitude lower drain leakage at 200 °C, accompanied by suppressed gate leakage and improved high‑temperature OFF‑state performance.

      Without field‑plate or other edge‑termination structures, the device with L_GD=30 μm achieves breakdown voltage over 3 kV and specific ON‑resistance of 206.84 mΩ⋅cm ², delivering competitive comprehensive power‑device performance.

      Combining PL characterization and drift-diffusion TCAD simulation, the mechanism is illustrated. Shallow Fe-related acceptor level (~0.8 eV) triggers thermally-activated leakage at high temperature, while deep-level intrinsic defects (2.4–3.1 eV) inside buffer layer trap thermally-excited carriers and block substrate-mediated leakage paths.

      The team verified epitaxial engineering of intrinsic-defect buffer layer as a feasible and effective technical route for high-voltage β-Ga₂O₃ power devices operating under harsh high-temperature conditions.

Conclusion

      In summary, we have demonstrated an effective strategy to suppress high-temperature OFF-state leakage in lateral β-Ga₂O₃ MOSFET by incorporating a semi-insulating β-Ga₂O₃ buffer layer. Through the ozone-assisted growth of the β-Ga₂O₃ buffer layer, in situ defect engineering is effectively realized, resulting in the formation of a high density of V_Ga and V_Ga-V_O within the buffer layer. These defects act as deep-level acceptors, enabling efficient compensation of thermally activated carriers and suppressing leakage pathways under elevated temperature operation. Consequently, the MOSFET with the buffer layer exhibits an ultralow leakage current of approximately 10⁻⁶ mA/mm at 200 °C, nearly two orders of magnitude lower than that of the device without a buffer layer. In addition, the device achieves a Vbr exceeding 3 kV and a RON,SP of 206.84 mΩ·cm². The design of epitaxial buffer engineering provides a viable and effective pathway toward realizing high-temperature and high-voltage β-Ga₂O₃ power devices for harsh-environment applications.