Enhancement Mode (E-Mode) AlGaN/GaN MOSFET With A/mm Leakage Current and ON/OFF Current

Postgate annealing (PGA) in N₂/O₂ atmosphere at 300°C for various annealing time is performed on enhancement mode AlGaN/GaN MOSFET fabricated using a self-terminating gate recess etching technique. After 45-min annealing, the device OFF-state leakage current decreases by more than two orders of magnitude and thus a low OFF-state leakage current of ´10-13 A/mm is obtained at room temperature, resulting in an excellent ON/OFF current ratio of ~10¹². At 250°C, the device still exhibits a low OFF-state leakage current of ~10^-9 A/mm and high ON/OFF current ratio of ~10⁸. Meanwhile, a strong correlation between the OFF-state leakage current and mesa isolation current is observed as we change the annealing time: 1) the lower the mesa isolation current and 2) the lower the OFFstate leakage current and thus the higher the ON/OFF current ratio. It is the suppression of the mesa isolation current owing to the passivation of atomic layer deposition Al₂O₃ that leads to the improvement of the OFF-state leakage current and ON/OFF current ratio after PGA. Besides, the device shows no obvious change in terms of its threshold voltage and maximum drain current after PGA.