300°C operation of normally-off AlGaN/GaN MOSFET with low leakage current and high on/off current ratio

300°C operation of a normally-off AlGaN/GaN metal-oxide semiconductor field-effect transistor (MOSFET) is successfully demonstrated, which is fabricated using a self-terminating gate recess etching technique. At 300°C, by employing a 15 nm-thick Al₂O₃ as the gate dielectric deposited by atomic layer deposition, the fabricated normally-off MOSFET exhibits a threshold voltage (V_th) of 3.2 V, a low off-state leakage current of ~10^-7 A/mm and a low forward gate leakage current of ~10^-7 A/mm. Thus, a high on/off current ratio of ~ 10⁶ is obtained. Furthermore, the normally-off MOSFET also exhibits small variations in terms of its V_th from room temperature to 300°C with a maximum relative variation of 6.7% in a such temperature range. These results make this normally-off AlGaN/GaN MOSFET very promising for high-temperature digital electronics.