Body Diode of 1.2kV SiC MOSFET: Unipolar and Bipolar Operation

Abstract

In this work, we investigate the Body Diode (BD) of a 40mOhm, 1.2kV SiC MOSFETs. We performed DC measurements and switching measurements, at Room Temperature (RT) and High Temperature (HT) (T=175°C), together with TCAD simulation and calibration. In switching measurements, we focused on the low side (LS) switch turn-on event, i.e., the BD turn-off event. We demonstrated that unipolar and bipolar BD can both be achieved with different VGS. With VGS=-5V, BD conducts in bipolar mode with carriers being injected via pn junction. This is rather well known in literature and is well characterized by the Negative Temperature Coefficient (NTC) of BD VF. Switching with BD VGS=-5V show strong reverse recovery-temperature dependent that caused by the augmented minority carrier injection at high temperature. Unipolar BD is achieved by channel conduction at VGS=0V and it is well characterized by BD VF - Positive Temperature Coefficient (PTC). Thanks to the unipolar nature, turn-on switching with BD VGS=0V show no reverse recovery-temperature dependent.