Numerical and experimental study of the mesa configuration in high-voltage 4H-SiC PiN rectifiers

The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study. Three geometrical parameters, i.e., mesa height, mesa angle and mesa bottom corner, are investigated by numerical simulation. The simulation results show that a deep mesa height, a small mesa angle and a smooth mesa bottom (without sub-trench) could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution. Moreover, an optimized mesa structure without sub-trench (mesa height of 2.2 μm and mesa angle of 20°) is experimentally demonstrated. A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm² are obtained from the fabricated diode with a 30-μm thick N^- epi-layer, corresponding to 85% of the ideal parallel-plane value. The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge.