A NEW APPROACH TO OPTIMIZING THE BASE PROFILE FOR HIGH-SPEED BIPOLAR-TRANSISTORS

This paper presents a new approach to optimizing the base profile of bipolar transistors for high-speed applications. Contrary to previous analyses that suggest that a graded profile is optimal, we show 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. © 1990 IEEE