Investigation of Unclamped Inductive Switch Characteristics in 4H-SiC MOSFETs With Different Cell Topologies

To investigate the unclamped inductive switch (UIS) characteristics, 1200 V silicon carbide (SiC) planar MOSFETs with four cell topologies of linear, current sharing linear, square, and hexagon are designed and manufactured. The experimental platform was built and tested. The results show that the single pulse avalanche energy density of the linear cell topology is 1.69 times higher than that of the square and 1.49 times that of the hexagon. Further, the UIS process is simulated by using physical simulation, which shows that the avalanche energy was concentrated near the corner of the P-base region in the UIS mode. From this, the avalanche energy distribution differences of the four cell topologies were analyzed and compared. A theoretical model of avalanche heating per unit area is proposed, which shows that the avalanche energy density is inversely proportional to the proportion of avalanche energy concentration region. This study may contribute to the cell topology design of SiC MOSFETs under the application scenario with high avalanche reliability requirements.