In this paper, a novel AlGaN/GaN HEMT structure with a P-GaN buried layer in the buffer layer and a locally doped barrier layer under the gate (PN-HEMT) is proposed to enhance its resistance to single event transient (SET) effects while also overcoming the degradation of other characteristics. The device operation mechanism and characteristics are investigated by TCAD simulation. The results show that the peak electric field and impact ionization at the gate edges are reduced in the PN-HEMT due to the introduced P-GaN buried layer in the buffer layer. This leads to a decrease in the peak drain current (I_peak) induced by the SET effect and an improvement in the breakdown voltage (BV). Additionally, the locally doped barrier layer provides extra electrons to the channel, resulting in higher saturated drain current (I_D,sat) and maximum transconductance (g_max). The I_peak of the PN-HEMT (1.37 A/mm) is 71.8% lower than that of the conventional AlGaN/GaN HEMT (C-HEMT) (4.85 A/mm) at 0.6 pC/µm. Simultaneously, I_D,sat and BV are increased by 21.2% and 63.9%, respectively. Therefore, the PN-HEMT enhances the hardened SET effect of the device without sacrificing other key characteristics of the AlGaN/GaN HEMT.

In this work, it is demonstrated for the first time that a negative gate voltage (V_GS) during off-state can enhance the single-event effect (SEE) hardness of the 100-V E-mode p-GaN HEMTs. When subjected to irradiation from Ta ions with linear energy transfer of 78.40 MeV/(mg/cm²), the single-event transient (SET) current peak during irradiation can be significantly decreased if a negative V_GS is applied, as opposed to using zero V_GS. Furthermore, a negative V_GS suppresses post-irradiation shifts in gate capacitance (C_G), threshold voltage (V_th) and off-state drain leakage current (I_DSS), indicating improved stability against SEE. Numerical simulations have been performed to offer a physical insight into the underlying mechanisms. It is found that a negative V_GS enables the simultaneous removal for radiation-induced holes and thus suppresses the SET current. The post-irradiation degradation of C_G, V_th and I_DSS are attributed to the radiation-induced acceptor-like traps at the Schottky junction, the AlGaN/GaN interface and the buffer layer, respectively.

To enhance the DC and RF performance of AlGaN/GaN HEMTs, a novel device structure was proposed and investigated through simulation. The key innovation of this new structure lies in the incorporation of an Al_0.7In_0.15Ga_0.15N back-barrier layer and an N-type locally doped AlGaN barrier layer (BD-HEMT), based on conventional device architecture. The Al_0.7In_0.15Ga_0.15N back-barrier layer effectively confines electrons within the channel, thereby increasing the electron concentration. Simultaneously, the N-type locally doped AlGaN barrier layer introduced beneath the gate supplies additional electrons to the channel, further enhancing the electron density. These modifications collectively lead to improved DC and RF characteristics of the device. Compared to the conventional AlGaN/GaN HEMT, BD-HEMT achieves a 24.8% increase in saturation drain current and a 10.4% improvement in maximum transconductance. Furthermore, the maximum cutoff frequency and maximum oscillation frequency are enhanced by 14.8% and 21.2%, respectively.