Simulation Analysis of Increase in ON-State Voltage of 4H-SiC Bipolar Devices Due to Single-Shockley-Stacking Faults

Mechanism of increase in the ON-state voltage of 4H-SiC PiN diodes due to the expansion of single-Shockley-stacking faults (1SSFs), so-called bipolar degradation, was investigated by performing a technology computer-aided design (TCAD) simulation. Electrical characteristics in 15-kV class PiN diodes with a 1SSF monolayer in a voltage-blocking layer were calculated while modeling the 1SSF as a quantum well (QW) for electron conduction. The simulation results clarified that a potential barrier formed by electrons trapped in the QW does not significantly deteriorate the current conduction under a low applied voltage due to hole current and recombination current paths. However, since the concentration of trapped carriers in the QW becomes extremely high especially when increasing the applied voltage, direct and Auger recombination occurs considerably around the 1SSF. This suppresses the conductivity modulation, and then the contribution of the hole current decreases, leading to significant disturbance of the current flow due to the potential barrier and large voltage drop at the 1SSF. Accordingly, the increase in the ON-state voltage of SiC bipolar devices is attributed to both electron trapping to the QW and enhanced carrier recombination around the 1SSF.