Trap-induced electrical degradation in edge-termination-hardened NiO/<i>β</i>-Ga2O3 heterojunction under 10 MeV fluence-dependent proton irradiations

Ultrawide bandgap beta-phase gallium oxide (β-Ga2O3) power devices have great potential in irradiation applications, yet the instability of their electrical performance induced by irradiation remains under investigation. This work examines the degradation of electrical performance in edge-termination-hardened nickel oxide (NiO)/β-Ga2O3 heterojunction p–n diodes (ETH-HJDs) subject to 10 MeV proton irradiation across a wide fluence range of 1011–1013 p/cm2. The results reveal interface and bulk trap-induced degradation with intriguing non-monotonic variations in forward conduction and reverse leakage currents—initially increasing and then decreasing with increased irradiation fluences. This abnormal phenomenon is unlikely due to irradiation-induced edge damage as the ETH design was implemented. Forward I–V curve modeling showcases an aggravated series resistance effect after irradiation, with the ideality factor rising from 1.07 to 1.24, indicating deteriorated interface properties. Capacitance–voltage (C–V) characterizations suggest that bulk traps caused by irradiation impact the carrier removal effect, evidenced by a carrier removal rate of 1070 cm−1 at a high proton fluence of 1 × 1013 p/cm2. Furthermore, deep-level transient spectroscopy reveals four distinct types of traps distributed at the interface or within Ga2O3 bulk contributing to the device leakage. These findings offer critical insights into the instability of electrical characteristics in high-performance NiO/β-Ga2O3 HJDs under proton irradiation.