Infulence of small emitter and contact non-uniformities on the current filamentation in 3.3-kV p+ - n- -n+ silicon diodes

We investigate the current filamentation behavior during reverse recovery in high-voltage 3.3-kV silicon p⁺ - n^- - n⁺ diodes with transient S-shape negative differential resistance characteristics. The transient I ^-bistability occuring in the reverse recovery period leads to a non-uniform current distribution in the diodes when they are turned off with a high current rate di/dt. In this paper we compare the filamentation behavior of a homogeneous quasi one-dimensional structure with diodes providing small contact and emitter non-uniformities. The formation of these high-current domains is studied by means of isothermal device simulation and the different characteristics are explained by analyzing the transient electric-field and current-density distributions in the devices