Different types of avalanche-induced moving current filaments under the influence of doping inhomogeneities

The influence of small doping inhomogeneities on the behavior of current filaments appearing in p+–n−–n+ diodes during the reverse-recovery period under extreme turn-off conditions is investigated. It is shown that depending on the strength and the distance between the inhomogeneities, different types of filament dynamics may appear, resulting in irregular or regular hopping or a continuously traveling filament. The hopping filament dynamics is essentially controlled by the long-range inhibitory effect of local plasma extraction, while the traveling filament is dominated by the mutual interaction of charge carrier generation and plasma extraction in the region between two neighboring inhomogeneities. Electrothermal simulations have shown that local heating induced by a traveling filament may result in the generation of a non-moving thermal-induced filament which can lead to destructive thermal runaway. The onset of thermal runaway is extremely sensitive to the thermal resistance of the contacts.