The interdependence between the collapse phenomenon and the avalanche breakdown in AlGaAs/GaAs power heterojunction bipolar transistors

An undesirable phenomenon which can occur in a heterojunction bipolar transistor (HBT) operating at high power density (and thus high junction temperature) is the collapse of current gain. The collapse manifests itself with a significant decrease of collector current in the transistor common-emitter current-voltage (I-V) characteristics. Previously, the interaction between the collapse and carrier ionization multiplication in the collector was only qualitatively described. In this study, we present a theoretical analysis modeling such interaction. From the calculated results, we establish that the previous qualitative description of the interdependence of the collapse and the avalanche breakdown, while being mostly accurate, requires modification.>