Investigation of interface, border and bulk traps of Al2O3/β-Ga2O3 MOS capacitors via O2 plasma treatment

While Gallium Oxide (Ga₂O₃) metal-oxide-semiconductor field-effect transistors (MOSFETs) hold great potential for high power applications, effective control of the MOS interface remains a subject of ongoing investigation. Previous studies always focused on interface traps, while overlooking the bulk and broader traps in dielectric layer. In this study, the effects of oxygen plasma treatment on the interface, border and bulk traps of Al₂O₃/β-Ga₂O₃ MOS capacitors were systematically investigated through high/low frequency C–V, hysteresis C–V, and forward-bias stress tests. The results showed that devices treated with 50 W plasma power for 1 min effectively passivated the interface dangling bonds and also improved the crystalline quality of Al₂O₃ dielectrics, exhibiting the lowest interface, border and bulk traps density. In contrast, excess plasma density or total treatment energy introduced etching defects, deteriorating the interface and dielectrics’ quality. The study demonstrates that appropriate oxygen plasma pretreatment provided an effective solution for the future application of high-performance β-Ga₂O₃ MOS devices.