Analyzing the Changes in the Third Quadrant Characteristics of SiC MOSFET Induced by Threshold Drift

The third quadrant (3rd-quad) of SiC MOSFETs is typically used for deadtime freewheeling, which improves the power density. Because the channel in the 3rd-quad may not be completely closed, the 3rd-quad characteristics are more or less influenced by threshold voltage drift. However, a comprehensive evaluation of the impact of threshold drift on the 3rd-quad characteristics remains to be completed. In this article, the effects of threshold drift on 3rd-quad characteristics are revealed, and the mechanisms behind the effects are discussed. The sensitivity of static and dynamic 3rd-quad characteristics to threshold voltage are studied under different off-state gate voltage, temperature, and p-base region resistance. Moreover, the explanation for the difference in sensitivity between devices is analyzed. The research provides guidance for both the application and chip design of SiC MOSFETs.