Single-Event Effects and Corresponding Nanoscale Microstructure in β-Ga₂O₃ UMOSFETs: Device Reliability and Failure Mechanism

β-Ga₂O₃ power transistors are highly attractive for applications in space power systems due to their low cost, high BFOM, and the high atomic displacement energy of the material itself. However, single-event effects (SEEs) induced by heavy ions in the space environment can lead to severe reliability issues in power devices, thereby causing failures of spacecraft. In this work, we systematically investigated the SEEs of vertical gallium oxide transistors under heavy-ion irradiation by employing β-Ga₂O₃ U-shaped trench-gate MOSFETs (UMOSFETs). Under irradiation by tantalum (Ta) ions with a linear energy transfer (LET) of 82.1 MeV·cm²/mg, the single-event burnout (SEB) voltage of the UMOSFETs reaches approximately 200 V. Meanwhile, we found that single-ion irradiation induces unique thermal melted pores at the bottom of the device's gate trench. These pores penetrate the epitaxial layer and oxide layer, and ultimately the metal electrode; such holes cause the device to undergo degradation and failure at a very low fluence (~2×106 ions/cm²) and relatively low bias voltage (~100 V).