Optimized P-emitter doping for switching-off loss of superjunction 4H-SiC IGBTs

This paper studied the effect of P-emitter concentration on the turn-off power loss (E off ) of superjunction 4H-SiC IGBTs (SJ IGBTs) via simulation. Two types of SJ IGBTs, with blocking voltages being 2.0 kV, and 5.5 kV respectively, were studied at various temperatures from 300 K to 500 K. It was found that two kinds of minimum E off , E off, min , emerged due to the differences of conductivity modulation in the pillar regions and the roles of the parasitic PNP transistor. For the 2 kV-class SJ IGBT, the concentration of excess carrier in the drift layer was varied with a peak value at moderate P-emitter doping level. And there was a catenary temperature dependence between EoJJ and P-emitter doping concentration owing to the interaction of hole and electron current. While for the 5.5 kV-class, the manifestation of E off, min emerged when higher degree of conductivity modulation occurred in the drift layer. And E off, min turned to appearing at high p-emitter doping level for lower operating temperature. Also the temperature-dependent fluctuation of E off for the 5.5 kV-class went up at high P-emitter doping concentration. These results can be valuable for the reference design rules of novel 4H-SiC SJ IGBTs and bring further improvement for the static and dynamic performances of devices.