Si IGBT and SiC MOSFET – Potentials and Limitations of Plasma Shaping versus Unipolar Switching in Medium Power Applications

For a trade-off between turn-off and on-state of power switches in medium and high power applications, it is crucial to consider the switching speed restrictions due to turn-off peak voltage. By varying the p-emitter efficiency and the front side plasma level of an IGBT, an $E_{\text{off}}-V_{\text{ce},\text{sat}}$ trade-off curve for a fixed turn-off peak voltage can be obtained. It is shown that a turn-off behavior similar to that of a SiC MOSFET can be achieved with an IGBT with low carrier confinement, but with the drawback of a higher on-state voltage drop. At low current operations, the losses dissipated by the SiC MOSET are lower, not only in the on-state, but also during turn-off. The charge carrier plasma in the IGBT reduces both $\mathrm{d}v/\mathrm{d}t$ and $\mathrm{d}i/\mathrm{d}t$ for lower current densities. Switching curves at the rim of the RBSOA and beyond show that there is no dynamic avalanche in the SiC MOSFET. However, a quasi-static clamping mode can be observed for both types of devices.