Characterization and optimization of AlGaN/GaN metal-insulator semiconductor heterostructure field effect transistors using supercritical CO₂/H₂O technology

The impact of supercritical CO₂/H₂O technology on the threshold-voltage instability of AlGaN/GaN metal-insulator semiconductor high-electron-mobility transistors (MIS-HEMTs) is investigated. The MIS-HEMTs were placed in a supercritical fluid system chamber at 150 ^°C for 3 h. The chamber was injected with CO₂ and H₂O at pressure of 3000 psi (1 psi≈6.895 kPa). Supercritical H₂O fluid has the characteristics of liquid H₂O and gaseous H₂O at the same time, that is, high penetration and high solubility. In addition, OH^- produced by ionization of H₂O can fill the nitrogen vacancy near the Si₃N₄/GaN/AlGaN interface caused by high temperature process. After supercritical CO₂/H₂O treatment, the threshold voltage shift is reduced from 1 V to 0.3 V. The result shows that the threshold voltage shift of MIS-HEMTs could be suppressed by supercritical CO₂/H₂O treatment.