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

Abstract

This paper studied the effect of P-emitter concentration on the turn-off power loss (Eoff) 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 Eoff, Eoff, 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 Eoff, min emerged when higher degree of conductivity modulation occurred in the drift layer. And Eoff, min turned to appearing at high p-emitter doping level for lower operating temperature. Also the temperature-dependent fluctuation of Eoff 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.