【Domestic Papers】He-induced semi-insulating microcolumns for high-voltage leakage current suppression in β-Ga₂O₃ Schottky barrier diodes

      The research team led by Professor Xin Ke Liu from Shenzhen University has published a paper titled He-induced semi-insulating microcolumns for high-voltage leakage current suppression in β-Ga₂O₃ Schottky barrier diodes in the academic journal Applied Physics Letters.

Background

      β-Ga₂O₃ features an ultra-wide bandgap of 4.8–4.9 eV and a theoretical breakdown electric field of 8 MV/cm, making it a highly competitive candidate for next-generation high-voltage power electronic devices. Schottky barrier diodes (SBDs), with their simple structure, low conduction losses, and fast switching speed, are among the key device architectures for Ga₂O₃ power electronics.

      However, conventional β-Ga₂O₃ SBDs can exhibit significant reverse leakage current under high reverse bias due to effects such as Schottky barrier lowering, which limits their breakdown voltage and practical engineering applications. Various approaches have been explored to improve the leakage characteristics of Ga₂O₃ devices, including epitaxial growth and device-structure optimization. Although reducing the carrier concentration in the drift layer can improve reverse-bias characteristics to some extent, it increases the difficulty of epitaxial growth and simultaneously degrades forward conduction performance.

      Junction barrier Schottky (JBS) diodes and trench MOS/MIS devices can suppress leakage current by modulating the electric field through charge coupling and the RESURF effect. However, JBS structures are constrained by the lack of stable p-type doping in β-Ga₂O₃, while trench-based devices involve relatively complex fabrication processes and higher manufacturing costs.

      Therefore, developing an SBD architecture that can effectively suppress high-voltage reverse leakage current while maintaining a simple fabrication process remains a key challenge in the field of Ga₂O₃ power electronics. In this work, the researchers propose a semi-insulating microcolumn-based SIMC-SBD architecture constructed through helium-ion implantation. The approach achieves low leakage current under high reverse bias without significantly increasing process complexity, addressing a gap in this particular device-engineering approach.

Abstract

      Local semi-insulating regions in β-Ga₂O₃ are critical for high-voltage devices, as they can regulate the interfacial electric field and improve leakage-current characteristics. The research team introduced a high concentration of acceptor-like defects into the n⁻-Ga₂O₃ matrix through helium-ion implantation, thereby forming an array of semi-insulating microcolumns in situ. These semi-insulating microcolumns effectively reduce the electric field near the Schottky junction, decrease the effective anode area in direct metal–semiconductor contact, and significantly suppress reverse leakage current.

      Through a combination of SRIM simulations, HR-TEM, XPS, UPS, and KPFM characterization, the researchers confirmed that He-ion implantation generates a large number of acceptor-like defects, including gallium vacancies (VGa) and interstitial helium atoms (Heᵢ). These defects compensate for free carriers and locally transform n⁻-Ga₂O₃ into a semi-insulating state, substantially reducing the electrical conductivity of the implanted Ga₂O₃ regions.

      In the fabricated Ga₂O₃ SIMC-SBD, the semi-insulating microcolumns occupied 28% of the total anode area. At a reverse bias of 1000 V, the reverse leakage current was reduced by nearly two orders of magnitude compared with that of a conventional SBD, while the device achieved a breakdown voltage of up to 1807 V. This architecture provides a simple and feasible approach for developing β-Ga₂O₃ SBDs that simultaneously achieve high breakdown voltage and low leakage current.

Highlights

      In-situ formation of semi-insulating microcolumn arrays: Helium-ion implantation is used to form semi-insulating microcolumn arrays in β-Ga₂O₃, dominated by acceptor-like defects such as VGa and Heᵢ, enabling localized conversion to a semi-insulating state. Multiscale characterization confirms that He-ion implantation increases the material work function and induces carrier compensation, revealing the evolution mechanism of implantation-induced defects.

      Significant suppression of reverse leakage current: Under a reverse bias of 1000 V, the SIMC-SBD achieves a reverse leakage current approximately two orders of magnitude lower than that of a conventional SBD, while maintaining a breakdown voltage of 1807 V.

      Clarification of the leakage-suppression mechanism: The semi-insulating microcolumns reshape the interfacial electric-field distribution and reduce the peak electric field near the interface. Meanwhile, they reduce the effective metal–semiconductor contact area of the anode, thereby limiting leakage-current pathways. The study elucidates the underlying mechanism responsible for leakage-current suppression.

Conclusion

      By introducing a high density of acceptor-like V_Ga and Heᵢ defects into Ga₂O₃ through helium-ion implantation, the researchers achieved the in-situ formation of semi-insulating microcolumns beneath the Schottky anode. These semi-insulating microcolumns suppress high-voltage reverse leakage current through two synergistic mechanisms: they modulate the electric-field distribution near the Schottky junction and reduce the interfacial electric field, while simultaneously reducing the effective metal–semiconductor contact area, thereby limiting leakage-current pathways.

      The fabricated SIMC-SBD achieved a breakdown voltage of 1807 V and a specific on-resistance of 4.1 mΩ·cm². At a reverse voltage of 1000 V, its leakage current was reduced by nearly two orders of magnitude compared with that of a conventional SBD, significantly lowering the off-state power consumption.

This defect-engineering-induced local semi-insulating strategy provides a new design approach for high-voltage β-Ga₂O₃ Schottky power devices.

Project Support

      This work was supported by the National Key Research and Development Program of China (2024YFE0205100), the Major Project of Guangdong Basic and Applied Basic Research Foundation (2023B0303000012), the Shenzhen Science and Technology Program (SGDX20240115101802004), the Shenzhen University Scientific Instrument Development Project (2024YQ003), and the Independent Research Project of the State Key Laboratory of Radio Frequency Heterogeneous Integration (2025007).