Investigation Into the Third Quadrant Characteristics of Silicon Carbide MOSFET

Owing to the superior performances, silicon carbide (SiC) metal oxide semiconductor field effect transistors (mosfets) attract a lot of attention. To increase the power density, it is desired to use the third quadrant (3rd-quad) characteristics of the mosfet rather than the externally paralleled Schottky diode for freewheeling during the deadtime. It has been known that the 3rd-quad is far more than a body diode, and the MOS channel is also an important part of it. The channel may be not fully closed and, therefore, play a significant role in the reverse conduction even when the gate is zero or negatively biased. However, a comprehensive study of the 3rd-quad characteristics is still to be conducted. In this article, experiments and simulations are conducted and a physical model is developed to explain the 3rd-quad characteristics of the SiC mosfet. It reveals how and why the 3rd-quad characteristics are affected by the gate voltage and the junction temperature. This article is helpful for not only the application of SiC mosfet but also the device design.