High-field fast-risetime pulse failures in 4H- and 6H-SiC pn junction diodes

We report the observation of anomalous reverse breakdown behavior in moderately doped (2–3×1017 cm−3) small‐area micropipe‐free 4H‐ and 6H‐SiC pn junction diodes. When measured with a curve tracer, the diodes consistently exhibited very low reverse leakage currents and sharp repeatable breakdown knees in the range of 140–150 V. However, when subjected to single‐shot reverse bias pulses (200 ns pulsewidth, 1 ns risetime), the diodes failed catastrophically at pulse voltages of less than 100 V. We propose a possible mechanism for this anomalous reduction in pulsed breakdown voltage relative to dc breakdown voltage. This instability must be removed so that SiC high‐field devices can operate with the same high reliability as silicon power devices.