Hao Yuan

The deployment of silicon carbide (SiC) power devices in aerospace applications is constrained by their unexpected susceptibility to single-event effects (SEEs), despite the inherent advantages of wide bandgap materials. In this work, we experimentally investigate the SEE mechanisms in in-house fabricated 1200 V SiC VDMOSFETs under heavy-ion irradiation using Ta ions with a LET of 75 MeV·cm²/mg. Real-time current monitoring, post-irradiation electrical characterization, and focused ion beam (FIB) analysis were employed to systematically examine device degradation and failure modes under various bias conditions. The results demonstrate a clear progression of damage with increasing bias voltage: no significant changes, single-event gate leakage degradation (SEGLD) at 100 V, single-event leakage current (SELC) in both I _d =I _g and I _d >I _g modes at 300–400 V, and catastrophic single-event burnout (SEB) at 500 V. Structural analyses reveal progressive deepening of gate oxide fractures, extension into the P+ source region, and eventual source metal melting, consistent with the observed electrical degradation. Notably, the threshold voltage remained stable throughout, suggesting that localized damage to limited unit cells has minimal influence on the global device threshold. These findings provide critical insights into SEE-induced degradation pathways in SiC MOSFETs and offer valuable guidelines for the design and radiation hardening of next-generation aerospace power systems.

In this paper, we propose a novel method for fabricating high-thermal-stability Ohmic contacts on 4H-SiC using a low-doping-concentration (2.5 × 10¹⁵ cm⁻³) n-type epitaxial layer. The method employs a tungsten/carbon (W/C) multi-nanolayer stacked structure combined with a 1200 °C rapid thermal process (RTP). The fabricated Ohmic contacts achieve a specific contact resistance ρ_c of 2.53 × 10⁻⁴ Ω·cm² at room temperature (RT) and 1.29 × 10⁻⁵ Ω·cm² at 500 °C. Furthermore, they exhibit excellent long-term operational reliability, maintaining stable performance during a 500 °C high-temperature test for 100 h in air without significant degradation. This method eliminates the need for ion implantation, avoiding lattice damage and reducing fabrication cost. The demonstrated thermal stability is highly desirable for elevated-temperature SiC-based devices and integrated circuits.

In this work, 4H-SiC p-i-n diodes with excellent single-pulse avalanche energy density (EAS) with positively beveled mesa termination have been demonstrated. The fabrication of this junction termination extension (JTE) obviates ion implantation and requires only etching process. With its uniform electric field and temperature distribution, the fabricated 4H-SiC p-i-n diodes show breakdown voltage (BV) of 886V (98.4% of the parallel-plane limit) and the inductive avalanche energy density of ~10.4J/cm²@1mH. Meanwhile, ruggedness of the avalanche breakdown has also been evidently promoted. The results confirm that this structure exhibits great capability potential in power applications.

In this paper the effects of 5 MeV proton irradiation on nitrided SiO₂/4H-SiC metal–oxide–semiconductor (MOS) capacitors are studied in detail and the related mechanisms are revealed. The density of interface states (Dit) is increased with the irradiation doses, and the annealing response suggests that the worse of Dit is mainly caused by displacement effect of proton irradiation. However, the X-rays photoelectron spectroscopy (XPS) measurement shows that the quantity proportion of breaking of Si≡N induced by displacement is only 8%, which means that the numbers of near interface electron traps (NIETs) and near interface hole traps (NIHTs) are not significantly changed by the displacement effect. The measurements of bidirectional high frequency (HF) C-V characteristics and positive bias stress stability show that the number of un-trapped NIETs and oxide electron traps decreased with increasing irradiation doses because they are filled by electrons resulted from the ionization effect of proton irradiation, benefiting to the field effective mobility (μ_FE) and threshold voltage stability of metal–oxide–semiconductor field-effect transistors (MOSFETs). The obviously negative shift of flat-band voltage (V_FB) resulted from the dominant NIHTs induced by nitrogen passivation capture more holes produced by ionization effect, which has been revealed by the experimental samples with different nitrogen content under same irradiation dose.