INFLUENCE OF IMPACT-IONIZATION-INDUCED BASE CURRENT REVERSAL ON BIPOLAR-TRANSISTOR PARAMETERS

In this paper we describe a set of measurements representing a complet e characterization of impact-ionization effects in bipolar transistors . We demonstrate that impact-ionization significantly influences the d ependence of base resistance on current and voltages applied to the de vice. A dc method for the simultaneous extraction of all parasitic res istances in bipolar transistors is presented. The method can separate the influence of current-crowding on the base resistance from that of base width and conductivity modulation; the collector parasitic resist ance is measured in the active region. Starting from the parameters ex tracted by means of these techniques, a complete and accurate circuit- model of impact-ionization effects can be defined.