Heavy-ion-induced degradation mechanisms and supercritical fluid recovery dynamics in Al₂O₃/β-Ga₂O₃ metal-oxide-semiconductor capacitors

This study investigated heavy-ion irradiation effects on Al₂O₃/beta-gallium (β-Ga₂O₃) metal-oxide-semiconductor capacitors (MOSCAPs), which serve as essential building blocks for metal-oxide-semiconductor field effect transistors (MOSFETs), and evaluated the restorative efficacy of N₂O-based supercritical fluid (SCF) treatment. Following tantalum (Ta) ion irradiation at a cumulative fluence of 4 × 10⁷ ions/cm², the net carrier concentration (N _d) degraded from 2.91 × 10¹⁶ to 1.92 × 10¹⁶ cm⁻³. The interface state density (D _it) and interface oxide trap charge density (N _iot) exhibited a slight decrease due to heavy-ion-induced defect restructuring, while the effective oxide charge density (N _eff) declined from 4.22 × 10¹¹ to 3.87 × 10¹¹ cm⁻² via electron capture by oxygen vacancies in the oxide layer. Irradiation-induced latent tracks and a reduction in trap energy level (φ _t) from 1.72 to 1.62 eV led to a tenfold increase in leakage current and reduced breakdown voltage, with trap-assisted tunneling identified as the dominant transport mechanism. To mitigate these effects, N₂O-based SCF treatments were employed to achieve recovery through mild nitridation and oxygen compensation. Initial SCF treatment increased φ _t to 1.78 eV, though persistent latent tracks limited the restoration of leakage characteristics. Subsequent SCF treatments further suppressed leakage current primarily by reducing electrically active trap density and passivating track-associated defects, despite a marginal decline in φ _t. Recovery saturation and N _eff polarity reversal were observed during prolonged exposure, indicating complex charge dynamics. These findings elucidated heavy-ion damage physics in Al₂O₃/β-Ga₂O₃ MOS structures and defined SCF operational boundaries, providing a critical reference for predicting the operational lifetime of future radiation-tolerant MOSFETs.