【Member Papers】Synergistic Effects of Oxygen Annealing and Low-fluence Kr Ion Irradiation on 4H-SiC and β-Ga₂O₃

Background

      The wide-bandgap semiconductor 4H-SiC and the ultra-wide-bandgap semiconductor β-Ga₂O₃, owing to their high critical breakdown electric fields, wide bandgaps, and excellent potential for operation at high-temperature and high voltage, have emerged as promising materials for next-generation high-power electronic devices. Schottky barrier diodes (SBDs) offer simple structures and fast switching, and are promising for radiation-intensive applications including space power systems, nuclear electronics, and particle detectors. However, their metal-semiconductor (M-S) interfaces and bulk deep-level defects are highly sensitive to high-energy particle irradiation, which can increase the ideality factor (n) and leakage current (I_R), while decrease the carrier concentration (N_D), thereby compromising long-term devices reliability.

      Previous studies have generally regarded irradiation primarily as a source of device degradation. However, recent studies indicate that appropriately controlled low-fluence heavy-ion irradiation can modify interface states and defect-charge distributions, thereby improving the forward-conduction and reverse-leakage characteristics of devices. Meanwhile, O₂ annealing can improve material quality and device performance by reducing interface defects in 4H-SiC and passivating or compensating oxygen vacancies (V_O) in β-Ga₂O₃. Nevertheless, the evolution of interface defects, bulk defects, and carrier-transport behavior under the combined effects of O₂ annealing and low-fluence heavy-ion irradiation remains insufficiently understood. In particular, few studies have directly compared of the improvement mechanisms of 4H-SiC and β-Ga₂O₃ devices subjected to identical treatment conditions. This knowledge gap hinders material-specific process optimization and limits the further development of highly reliable power devices for extreme radiation environments.

Highlights

      Establishment of a direct comparative framework for 4H-SiC andβ-Ga₂O₃ ​ SBDs under identical processing and irradiation conditions.By integrating SRIM simulations, I-V and C-V measurements, DLTS, and TCAD simulations, the relationships among energy deposition, defect evolution, and electrical performance were systematically established. This framework clarifies the physical origins of the distinct responses observed in the two wide-bandgap materials under identical treatment conditions.

      Identify the distinct physical mechanisms underlying the performance improvements. In 4H-SiC, interface-state passivation, reflected by an approximately 74% reduction in Nss, is the dominant mechanism, mitigating Fermi-level pinning and barrier-height inhomogeneity. In β-Ga₂O₃, a dual mechanism—bulk oxygen-vacancy (V_O) passivation, evidenced by an approximately 92% reduction in the E2 trap concentration, together with a shift in the interface-state energy level from 0.14 to 0.20 eV—jointly suppresses trap-assisted and field-enhanced leakage pathways. This mechanistic analysis provides a clear physical explanation for the simultaneous improvements in forward and reverse characteristics.

      Based on these findings, we propose a material-specific optimization framework.Interface engineering should be prioritized for 4H-SiC, whereas bulk-defect passivation combined with interface-state engineering should be emphasized for β-Ga₂O₃. This material-specific strategy provides practical guidance for enhancing the radiation tolerance and operational reliability of wide-bandgap power devices in extreme environments.

Conclusion

      This work comparatively investigates the impact of combined O₂ annealing and low-fluence Kr ion irradiation on the electrical performance of 4H-SiC and β-Ga₂O₃ SBH. Both devices exhibit a consistent suppression of J_R and an improvement in rectification characteristics after the synergistic treatment, demonstrating the effectiveness of the proposed processing. Notably, the magnitude of J_R reduction is more pronounced in β-Ga₂O₃ devices, indicating a stronger sensitivity to bulk defect modulation. Detailed N_SS extraction and DLTS characterization reveal that the underlying physical mechanisms of the performance improvement are fundamentally different. In the 4H-SiC SBDs, although irradiation induces bulk defects, the dominant factor is the substantial improvement in M-S interface state density quality. In contrast, the enhancement in β-Ga₂O₃ devices is primarily governed by suppression V_O-related defects via O₂ annealing. These results demonstrate that the combined treatment is advantageous for both material systems but operates through distinct pathways: interface engineering for 4H-SiC and bulk defect passivation for β-Ga₂O₃.This insight provides crucial guidance for future process optimization and reliability enhancement in wide-bandgap semiconductor devices.