Modelling Bipolar Transistor Second Breakdown During Turn-Off by Solution of the Fundamental Device Equations

Numerical simulations have been made of the turn-off of two-dimensional power bipolar transistor structures, under inductive loading, by alternate solution of the fundamental device equations and the circuit equations at each time step. The results have shown that current spreading reduces the magnitude of the electric field in the collector produced by the space charge of mobile electrons, so leading to improved reverse bias second breakdown performance. Removal of the central portion of the emitter effectively increases the current spreading and gives a further reduction in the space charge induced field.