Dynamic Transients and Reliability of High-Voltage Silicon & 4H-SiC Bipolar Junction Transistors Under Avalanche and Short-Circuits

This paper explores the dynamic characteristics and performance of two commercial bipolar junction transistors (BJTs) with the highest voltage ratings in class for each material: 800 V, 20 A Silicon BJT and 1.7 kV, 15 A 4H-SiC BJT. The investigation focuses on high current switching, unclamped inductive switching and short circuit conditions. Clamped inductive switching tests have been conducted using various load inductors and switching rates, at 800 V and maximum collector current of 14 A. In the unclamped inductive switching test, the stress level is increased by either extending the pulse length or increasing the DC-link voltage until the device fails. As for the short circuit test, the DC-link voltage is gradually increased until the device reaches its failure point. The dynamic transient measurements reveal that 4H-SiC BJTs outperform their Silicon counterparts. They exhibit higher current gain with a magnitude ten times higher than the Silicon counterpart. Notably, Silicon BJTs display significant delays in both turn-ON and turn-OFF transitions when compared to the 4H-SiC BJT leading to increased losses.