【International Papers】Investigation of Oxygen Vacancies and Reverse Leakage Suppression in High-Breakdown Vertical Ga₂O₃/4H-SiC Schottky Rectifiers

      Researchers from the Kwangwoon University have published a dissertation titled "Investigation of Oxygen Vacancies and Reverse Leakage Suppression in High-Breakdown Vertical Ga₂O₃/4H-SiC Schottky Rectifiers" in ISPSD 2025.

Background

      Gallium Oxide (Ga₂O₃) has emerged as a transformative material for next-generation high-power electronic devices, owing to its ultra-wide bandgap (~4.8 eV), high breakdown field (~8 MV/cm), and the feasibility of large-area wafer growth. These characteristics position Ga₂O₃ as a strong candidate for high-efficiency power switching applications. However, several fundamental limitations, such as its low thermal conductivity, continue to pose challenges for the practical application of Ga₂O₃ power devices. The low thermal conductivity of Ga₂O₃ results in self-heating, which degrades the electrical performance and can lead to premature failure of devices incorporating Ga₂O₃. To mitigate the self-heating effect, various techniques have been proposed, including the use of heterogeneous integration with high thermal conductivity substrates. The heterogeneous integration of Ga₂O₃ with SiC has proven to be an effective approach to overcoming Ga₂O₃’s thermal limitations. Although the superior heat dissipation performance of Ga₂O₃/SiC has been demonstrated, the formation of non-stoichiometric Ga₂O₃ layers during deposition introduces V_O-related defects, which degrade device performance. Although various studies have investigated Ga₂O₃ defect behavior, the precise role of oxygen vacancies in reverse leakage mechanisms remains poorly understood. In this work, a comprehensive investigation was conducted into the relationship between oxygen vacancy concentration, leakage characteristics, and blocking voltage performance in Ga₂O₃/SiC Scottky barrier diodes (SBDs). Through controlled high-temperature oxygen annealing, it was demonstrated that oxygen vacancy suppression significantly enhanced the blocking capability, enabling record-high BV performance (>3000 V) in Ga₂O₃/SiC SBDs. This study provides new insights into defect-driven reverse leakage mechanisms and offers practical defect engineering strategies for future ultra-wide bandgap (UWBG) power device applications.

Abstract

      In this study, the impact of oxygen vacancies (V_O) on the reverse leakage characteristics and breakdown voltage (BV) of Ga₂O₃/SiC Schottky barrier diodes (SBDs) was investigated. Using Deep Level Transient Spectroscopy (DLTS) and reverse leakage analysis, it was confirmed that oxygen vacancies were a key limiting factor, significantly reducing the blocking capability and increasing leakage current in Ga₂O₃- based power devices. To mitigate these detrimental effects, high-temperature oxygen annealing (900 ℃) was implemented, effectively suppressing oxygen vacancy formation. As a result, the dominant leakage current mechanism transitioned from Schottky emission (SE) to variable range hopping (VRH) under high voltage conditions, enabling the fabrication of high-performance Ga₂O₃/SiC SBDs with a BV exceeding 3000 V. This study not only provided valuable insights into defect engineering strategies, but also established a solid foundation for optimizing ultra-wide bandgap (UWBG) power devices, paving the way for next-generation high-efficiency power switching applications.

Fig. 1. (a) Schematic cross section of Ga₂O₃/SiC SBD. (b) Carrier concentration vs. depletion width calculated from capacitance-voltage method for non-annealed, N₂-annealed and O₂-annealed samples.

Fig. 2. (a) Forward J-V characteristics of non-annealed, N₂-annealed and O₂-annealed Ga₂O₃/SiC SBDs in linear scale. (b) Reverse breakdown voltage (BV) of three types of SBDs.