Giant burst of impact ionization in a p-n junction of the 6H-SiC polytype

A study of the electron component of impact ionization in the p+-n−-n+ junction in the 6HSiC polytype made it possible to detect a giant burst of impact ionization and origination of an extra early avalanche breakdown. The electric field of this breakdown is lower by ∼20% than the electric field of the breakdown arising as a result of a steady development of the impact ionization. It is of interest that this phenomenon occurs abruptly, without any apparent causes, in particular, without an increase in the dark current characteristic of a prebreakdown state of the p-n junction. Conditions for origination of an unusual breakdown and its properties made it possible to assume that there are nonlinear processes that give rise to a streamer. In the p-n junction plane, the anomalous breakdown is seen as a narrow glowing track with a width of ≈10 μm. This effect takes place in the conditions of the Wannier-Stark ladder of states. The latter can stimulate a local accumulation of charge and formation of a streamer structure.