The 4H-SiC VDMOSFET demonstrates a high reverse breakdown voltage (BV) due to the JFET region but experiences relatively high on-resistance (R_on). A widely adopted method to reduce the R_on is to uniformly increase the doping concentration of the JFET region, which results in a trade-off that reduces the BV. This study proposes a method to optimize the segmentation of the JFET region by selectively increasing the doping concentration using ‘total doping’, ‘half-doping’, and ‘quarter-doping’. The optimized quarter segment with a specific doping concentration slightly reduces BV, but the sharp decrease in specific on-resistance (R_on,sp) results in a 105% improvement in the performance index, Baliga’s Figure of Merit (BFOM). This research suggests the potential for electrically superior designs by modifying the doping concentration in the JFET region of conventional VDMOSFET structures.

In this work, we have investigated the effect of a 30-min thermal anneal at 550℃ on the electrical characteristics of neutron-irradiated 4H-SiC MOSFETs. Thermal annealing can recover the on/off characteristics of neutron-irradiated 4H-SiC MOSFETs. After thermal annealing, the interface-trap density decreased and the effective mobility increased in terms of the on-characteristics. This finding could be due to the improvement of the interfacial state from thermal annealing and the reduction in Coulomb scattering due to the reduction in interface traps. Additionally, in terms of the off-characteristics, the thermal annealing resulted in the recovery of the breakdown voltage and leakage current. After the thermal annealing, the number of positive trapped charges at the MOSFET interface was decreased.