Defect Engineering in β-Ga2O3 Schottky Barrier Diodes via Proton Irradiation and Subsequent Low-Temperature Supercritical Fluid Treatment

Abstract

This study proposes a defect engineering strategy that combines low-fluence proton irradiation for leakage current (J_r) suppression and subsequent low-temperature supercritical fluid (SCF) treatment for forward conduction characteristic restoration in β-Ga₂O₃ Schottky barrier diodes (SBDs) with and without NiO guard rings. Mechanistically, the results reveal that proton irradiation and subsequent SCF treatment are not the inverse of each other, as the former primarily introduces gallium vacancies (V_Ga), whereas the latter mainly passivates oxygen vacancies (V_O). On the one hand, for proton irradiation, the introduction of V_Ga reduces the net carrier concentration (N_D – N_A), leading to a significant decrease in J_r, accompanied by an increase in specific on-resistance (R_on,sp). On the other hand, for subsequent SCF treatment, the passivation of V_O effectively enhances electron mobility rather than substantially restoring N_D – N_A, thereby maintaining J_r at the irradiated level and considerably reducing R_on,sp. Consequently, through the above defect modulation in bulk β-Ga₂O₃, SBDs simultaneously achieve a decrease in J_r from 1.16 × 10^–5 to 2.01 × 10^–8 A·cm^–2 at –200 V, a moderate increase in R_on,sp relative to their unirradiated counterparts, and a higher on/off current ratio from 2.28 × 10⁷ to 5.69 × 10⁹ at –200 V. Furthermore, this strategy substantially diminishes the effectiveness of the NiO guard ring in reducing J_r. These findings highlight the potential of this defect engineering as an effective strategy for fabricating high-performance β-Ga₂O₃ SBDs.