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 (Nd) degraded from 2.91 × 1016 to 1.92 × 1016 cm−3. The interface state density (Dit) and interface oxide trap charge density (Niot) exhibited a slight decrease due to heavy-ion-induced defect restructuring, while the effective oxide charge density (Neff) 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 (φt) 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 φt 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 φt. Recovery saturation and Neff 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.