Normally-off AlGaN/AlN/GaN HEMT with a composite recessed gate

Abstract As we all know, the normally-off HEMT is very important to the safety of power electronic systems. To increase the threshold voltage of the device, this article proposes to cover Al2O3 on the recessed P-GaN to form the recessed p-GaN HEMT covered with Al2O3. Through simulation calculation, covering Al2O3 on P-GaN can effectively increase the threshold voltage, but the saturation current and transconductance will be severely reduced. Therefore, this article optimizes the structure and proposes a composite recessed-gate HEMT for the first time. It can obtain high saturation current and high transconductance while maintaining a high threshold voltage. Compared with the recessed p-GaN HEMT covered with Al2O3, the transconductance and saturation current of the composite recessed-gate HEMT are increased by 13.14% and 121.33%, respectively, while the threshold voltage is only reduced by 4.44% (4.3 V). In addition, the gate dielectric has a greater impact on device performance. Therefore, this paper analyzes the influence of the thickness of the Al2O3 layer on the device through theoretical calculations and obtains the optimal value of the thickness. (T1 = 18.3 nm, Vth = 4.5 V, Isat = 456 mA/mm). The results show that the composite recessed gate has broad application prospects in the next generation of normally-off power device applications.