Modeling of the critical current density of bipolar transistors with retrograde collector doping profile

Advanced bipolar transistors used for high speed integrated circuits tend to drive high current density. As a result, base-widening occurs and device performance degrades. One of the methods to alleviate the base-widening is to form retrograde collector profiles. In this paper, we have derived for the first time the model of the critical current density of bipolar transistors with retrograde collector profiles. To verify the model, we performed extensively device simulation for two different collector profiles. Results from the model were compared with those of device simulation. The model derived shows a good agreement with device simulation over a V/sub CB/ bias range of 1-4 V.