Reliability of SiC MPS Diodes Under Non-Repetitive Forward Surge Current

Abstract

Silicon Carbide (SiC) Merged PiN-Schottky (MPS) diodes have the benefit of conduction modulation under high current events while achieving low forward voltage and zero reverse-recovery under normal operations. Thus, the SiC MPS diodes can sustain surge currents several times larger than their average current rating, avoiding oversizing components and resulting in a more compact power electronic device. Two SiC MPS diodes were evaluated using a non-repetitive surge current testbed that delivers a square current pulse of 800 A. Five devices from each group were subjected to a ten µs current pulse every 20 seconds. The first device from each group started at lower current levels and was increased until device degradation occurred. Subsequent devices were then tested at the highest current level until degradation. Both groups have sustained currents up to 2.5 times their rated surge current rating. These devices were subjected to several thousand pulses, and their electrical characteristics, such as forward IV and reverse blocking voltage, were measured between testing intervals. Device degradation was observed as the reverse-blocking voltage has significantly decreased from preliminary measurements, but no degradation of the forward-IV curve was observed. The collected data demonstrate the device’s ability to operate under non-repetitive surge current events. Each device has sustained several hundred pulses above their rated surge current rating before any sign of degradation was detected. Device degradation becomes apparent when the leakage current increases as the MPS diode is blocking voltage. They eventually become prone to short-circuit failure due to a reduced reverse blocking voltage capability.