Cause of Forward Voltage Degradation for 4H-SiC PiN Diode with Additional Process

The forward voltage degradation in 4H-SiC PiN diodes with a simplified process and that in 4H-SiC pin diodes with additional processes are investigated. Photoluminescence images were also observed to identify the cause of forward voltage degradation. The forward voltage degradations of 4H-SiC PiN diodes with additional processes were larger than those with a simplified process. Observing photoluminescence images of diodes after a current stress test showed that less than 25% of Shockley-type stacking faults in 4H-SiC PiN diodes with a simplified process are caused by half-loop dislocations, which are generated not only in the additional processes but also in the whole device fabrication process. With additional processes, those rates are over 65%, which may be reduced by eliminating half-loop dislocations due to the optimization of the process condition and sequence.