Robust 800 K operation of AlInN/GaN HEMTs enabled by O2-based supercritical fluid treatment

We demonstrate high-temperature operation of Al0.83In0.17N/GaN high-electron-mobility transistors (HEMTs) at 800 K (∼527 °C) enabled by a post-fabrication supercritical fluid (SCF) treatment. NH3-based SCF (NH3-SCF) and O2-based SCF (O2-SCF) processes are systematically compared, showing that O2-SCF provides more effective oxidative passivation for interface engineering under extreme-temperature conditions. The O2-SCF treatment suppresses off-state leakage current by more than five orders of magnitude at room temperature and over two orders at 800 K, while increasing on-current by 30%–40% and reducing on-resistance from 10 to 8 Ω mm. The O2-SCF devices exhibit a subthreshold swing of 64 mV/dec and an on/off current ratio of 1012 at room temperature, retaining 230 mV/dec and 104 at 800 K, among the best reported for III-nitride HEMTs operating above 500 °C. These results demonstrate that O2-SCF is an effective post-fabrication strategy for improving interface quality and mitigating performance degradation at elevated temperatures in Al0.83In0.17N/GaN HEMTs, with potential for electronics in harsh environments.