Mitigating the effect of traps in p-GaN HEMTs through field plate and doping optimization

This work presents a complete analysis of normally-off p-GaN High Electron Mobility Transistors (HEMTs) with field plate using TCAD simulations in conjunction with physics-based analytical model. The study focuses on maximizing the breakdown voltage ( VBR ) through the integrated optimization of field plate (FP) length and Magnesium (Mg) doping concentration in the p-GaN cap layer under the influence of thermally assisted traps. The analyses were performed taking the reported experimental values of Mg and TAT (Trap Assisted Tunneling) concentrations. Implementation of the field plates successfully suppresses the crowding of electric field and enhance the channel breakdown voltage. The numerical length of the field plate is optimized for the highest breakdown voltage which was achieved at 978V when the field plate length (LFP) was 1.5 μ m in combination with high Mg doping.TCAD results also reveal that, Mg concentration significantly modulates the device’s threshold voltage ( VTH ), power density and leakage current. Explicitly, increasing the parametric value of Mg active concentration to 1× 10¹⁸ cm⁻³ increases the DC peak output current from 12 mA/mm to a saturation value of 67 mA/mm for V GS = 10V, while shifting the threshold voltage VTH from 4.91V to 1.6V. Furthermore, the TCAD results are compared with a physics-based analytical models specially developed for p-GaN HEMTs. These comparisons demonstrate strong agreement between the TCAD and the theoretical results in terms of DC characteristics for the proposed device. To the best of the authors’ knowledge, the combined optimization of field-plate length and Mg doping under trap-assisted tunneling conditions has not been previously investigated in detail. With the analytical cross-validation against experimentally-calibrated TCAD simulation, this approach also offers various performance parameter configurations, helping designers select the ideal combination for reliable high-power applications.