A new approach to optimizing the base profile for high-speedbipolar transistors

It is shown using first-order analytical analysis and extensive device simulations that, for a given base resistance and peak base doping, a uniform base profile gives a higher cutoff frequency than a graded profile. This result is explained by the narrower base width that can be achieved with a uniform profile, which more than compensates for the lack of the aiding electric field present in graded-base transistors