Enhancement Mode (E-Mode) AlGaN/GaN MOSFET With $10^{-13}$ A/mm Leakage Current and $10^{12}$ ON/OFF Current Ratio

Postgate annealing (PGA) in N
₂
/O
₂
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
$\sim 10^{-13}$
A/mm is obtained at room temperature, resulting in an excellent ON/OFF current ratio of
$\sim 10^{12}$
. At 250 °C, the device still exhibits a low OFF-state leakage current of
$\sim 10^{-9}$
A/mm and high ON/OFF current ratio of
$\sim 10^{8}$
. 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 OFF-state 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 Al
₂
O
₃
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.