Mitigating Plasma Etch-Induced Negative Charge Trapping in 2.7 kV β-Ga₂O₃ (001) Trench Schottky Barrier Diodes Using H₃PO₄ Treatment

Stable β-Ga₂O₃ (001) trench Schottky barrier diodes (TSBDs) with a Baliga’s figure-of-merit (BFOM) of 0.7 GW cm^–2 were demonstrated by reducing the Al2O3/Ga₂O₃ interface state trap density using a H₃PO₄ surface treatment during device fabrication. TSBDs with fins oriented along different directions have been studied, wherein devices with [010] fin orientation exhibited a low specific on-resistance (R_on,sp) of 11 mΩ cm² and a breakdown voltage (V br) of up to 2.7 kV with H₃PO₄ treatment. Reliability testing using sequential voltage stress up to a reverse bias of −1.2 kV showed a degradation in R_on,sp by 20% in untreated devices but only by 9% in those with the H₃PO₄ surface treatment. TCAD simulations confirm that the H3PO4 treatment mitigates the density of negative interface charges, highlighting the effectiveness of the acid treatment in controlling defect-mediated instabilities. Furthermore, high-temperature bias stress tests demonstrated that [010]-oriented TSBDs achieved superior thermal and electrical stability after the treatment, eliminating the 10% R_on,sp increase observed in untreated devices. These results establish H3PO4 surface treatment as an effective strategy for enhancing the robustness of β-Ga₂O₃ power devices under combined thermal and electrical stress.