Simulation and optimization of high breakdown double-recessed 4H-SiC MESFET with metal plate termination technique

In this paper a new high breakdown voltage (VBR) double-recessed 4H-SiC MESFET with metal plate (DRMP-MESFET) structure for reliable high power and RF applications is proposed. The maximum electrical field of the MESFET gate is clamped after surface depletion layer punch through to the metal plate (MP). The influence of MP structure on the breakdown voltage and cut-off frequencies of the DRMP-MESFET was studied by numerical device modeling. The optimized results showed that the VBR of the proposed structure with metal plate is 95% and 55% larger than that of the 4H-SiC double-recessed MESFET without metal plate (DR-MESFET) and conventional recessed-gate MESFET (R-MESFET), respectively, while maintaining almost the same saturation drain current characteristics. A maximum 12.6 W/mm output power density of the proposed structure with metal plate is reached compared to 6.1 W/mm and 4.4 W/mm for the DR-MESFET and R-MESFET, respectively, which means about 107% and 186% larger output power. Also, cut-off frequencies (fTfT) of 14.7 GHz and 16.2 GHz and maximum oscillation frequencies (fmax) of 54.3 GHz and 64.1 GHz for the 4H-SiC DRMP-MESFET and DR-MESFET are obtained compared to 11 GHz and 40 GHz for that of the R-MESFET structure, respectively. The simulation results reveal that a 95% improvement in VBR can be obtained with a metal plate while not significantly reducing its cut-off frequency.