Dynamic avalanche in bipolar power devices

In bipolar power devices, remaining plasma is extracted during turn-off. In high-voltage devices, even at moderate conditions dynamic avalanche caused by the free carriers appears. Strong dynamic avalanche leads to filament formation. The effect must not be destructive as long as the filaments can move. Effects which are common in the bipolar devices GTO, GCT, IGBT and power diode are investigated, and specific effects of each device are considered. In every case, the decisive effects for dynamic avalanche sustainability happen at the junction opposite to the blocking pn-junction.