【Member Papers】Interfacial rare-earth oxide-enabled X-ray-tolerant Ga₂O₃ MIS Schottky barrier diodes with significant reverse leakage current suppression

Background

      Spacecraft and nuclear power systems demand power semiconductors with both high breakdown voltage and ionizing radiation resistance. β-Ga₂O₃ with an ultra-wide bandgap of 4.8 eV is ideal for harsh-environment electronics. Conventional Ni/β-Ga₂O₃ Schottky diodes lack dielectric interlayers; X-ray irradiation generates massive interface defects, raising leakage current and degrading blocking capability. Rare-earth Gd₂O₃ features high dielectric constant and strong X-ray attenuation, yet its dual function of boosting breakdown and radiation tolerance remains underexplored. No systematic quantitative analysis on interface traps and Poole-Frenkel transport after irradiation has been reported, and no complete MIS diode architecture combining low on-resistance, kV-class breakdown and X-ray immunity exists, forming an obvious research gap for radiation-hard Ga₂O₃ power devices.

Abstract

      Power electronic devices operating in radiation-rich environments, such as space and nuclear facilities, require both high breakdown voltage and radiation tolerance. Gallium oxide (Ga₂O₃) offers an ultra-wide bandgap and a high critical electric field, but its electrical stability can be affected by X-ray-induced charge trapping and defect states. Here, we introduced an ultrathin rare-earth Gd₂O₃ interlayer to fabricate X-ray-tolerant Ni / Gd₂O₃ / β-Ga₂O₃ metal-insulator-semiconductor (MIS) Schottky barrier diodes (SBDs). This interfacial engineering strategy increased the breakdown voltage from 290 V for the conventional Ni / β-Ga₂O₃ SBD to 1001 V for the MIS SBD while maintaining a low specific on-resistance of 2.6 mΩ·cm². Remarkably, after X-ray irradiation, the Gd₂O₃-interlayer MIS SBDs exhibited stable forward characteristics and a three-order-of-magnitude suppression of reverse leakage current at -100 V, contrary to the degradation behavior observed in conventional SBDs. Frequency-dependent conductance analysis revealed that the leakage suppression originated from a reduced interface trap density rather than drift-layer carrier compensation. Temperature-dependent current-voltage analysis confirmed Poole-Frenkel emission as the dominant leakage mechanism, with the extracted emission barrier increasing from 0.73 to 1.33 eV after irradiation, indicating more difficult trap-assisted carrier emission, which also contributed to the suppressed reverse leakage current. Furthermore, the high-atomic-number rare-earth Gd₂O₃ interlayer may modify local X-ray energy deposition near the interface, which is consistent with the reduced contribution of interfacial trap states to leakage transport. These findings highlight rare-earth oxide interfacial engineering as a promising route to simultaneously achieve high breakdown capability and X-ray irradiation tolerance in Ga₂O₃ power devices for harsh-environment applications.

Highlights

      Propose ultrathin Gd₂O₃rare-earth interlayer engineering to construct radiation-hard Ni/Gd₂O₃/β-Ga₂O₃ MIS Schottky diodes.

      Realize breakdown voltage boosted from 290 V to 1001 V with specific on-resistance kept at 2.6 mΩ·cm².

      Achieve three orders of magnitude reverse leakage suppression under -100 V after X-ray irradiation with stable forward performance.

      Clarify dual mechanism: reduced interface trap density and elevated Poole-Frenkel emission barrier induced by high-Z Gd₂O₃ X-ray energy modulation.

Conclusion

      In summary, we reported an interfacial engineering strategy based on an ultrathin rare-earth Gd₂O₃ interlayer in Ni / Gd₂O₃ / β-Ga₂O₃ MIS SBDs to effectively enhance the device blocking capability and improve the device X-ray irradiation tolerance. After irradiation, the MIS SBDs exhibited nearly unchanged forward characteristics, including V_on and R_on,sp with slight V_br degradation. Notably, the reverse leakage current was suppressed, in contrast to conventional Ni / β-Ga₂O₃ SBDs. Frequency-dependent conductance and C-V measurements revealed a reduced D_T and only minor changes in the overall drift-layer carrier concentration, indicating that leakage current suppression originates from a modified near-interface trap response rather than drift-layer carrier compensation. J-V-T analysis confirmed that Poole-Frenkel emission dominated the reverse leakage transport through trap states in the highfield depletion region. The increased emission barrier after irradiation suggested that carrier emission from trap states became more difficult, thereby contributing to the suppressed leakage current. In addition, the high-Z rare-earth Gd₂O₃ interlayer may locally modify X-ray energy deposition near the interface, consistent with the reduced contribution of interfacial trap states to leakage transport. These findings demonstrate that rare-earth oxide interfacial engineering is an effective strategy for simultaneously improving breakdown capability and x-ray irradiation tolerance in β-Ga₂O₃ SBDs for harsh-environment power electronics.

Project Support

      This work was supported by the National Natural Science Foundation of China under Grant 62171396, the Shenzhen Science and Technology Program under Grant JCYJ20240813145617023.