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The mechanisms of bipolar degradation in silicon carbide BJTs are investigated and identified. Bipolar degradation occurs as result of stacking fault (SF) growth within the low-doped collector region. A stacking fault blocks vertical current transport through the collector, driving the defective region into saturation. This results in considerable drop of emitter current gain if the BJT is run at a reasonably low collector-emitter bias. The base region does not play any significant role in bipolar degradation. Long-term stress tests have shown full stability of large-area high-power BJTs under minority carrier injection conditions provided the devices are fabricated using low Basal Plane Dislocation (BPD) material. However, an approximately 20% current gain compression is observed for the first 30-60 hours of burn-in under common emitter operation, which is related to instability of surface recombination in the passive base region.

Large (4.3 mm2) area SiC BJTs were demonstrated with a current gain of 117 and a specific on-resistance of 2.8 mΩcm2. The open-base and open-emitter breakdown voltages are stable and with margin sufficient for 1200 V blocking. Fast and tail-current free switching behaviour was shown with rise- and fall-times in the range of 10-30 ns and the SiC BJTs were shown to be rugged in short-circuit and unclamped inductive switching.

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