1200-V 4H-SiC Merged p-i-n Schottky Diodes With High Avalanche Capability

In this article, the avalanche capability of the 1.2-kV 4H-SiC junction barrier Schottky (JBS) and merged p-i-n Schottky (MPS) diodes is investigated through simulation and experiments. For MPS diodes, the width of the wide P+ region ( W) is found to have great effects on the device avalanche capability. MPS diodes with varied W-values (3-20 mu m) and JBS diode are designed and fabricated, and their avalanche energy/current capability is testedwith unclamped inductive switching tests. The experimental results show that the MPS diode has an optimized avalanche capability at W = 8-mu m design. Simulation study reveals that the avalanche current is mainly distributed at the edges of the P+ regions in the JBS/MPS diodes as a result of the curvature-effect-induced electric field crowding. The localized current crowding and unbalanced current distribution in the avalanche mode contribute to a reduced effective power dissipation area and a weaker avalanche capability. The current nonuniformity coefficient (k) is used to characterize the severity of the current unbalance, and it is found that k declines as W increases when W = 3-8 mu m and then gets increased when W exceeds 8 mu m. Both the experimental and simulation results indicate that the MPS diode is superior to the JBS diode in avalanche capability, and the width of the wide P+ region in the MPS diode has an optimal design (8 mu m in this article) which corresponds to the alleviated current crowding issue and 9%-19% improvement of the avalanche capability.