A means to determine the doping profile minimizing base transit time in a bipolar transistor is presented, assuming that the width of (he neutral base is held constant. It is found that the optimum profile is not close to the exponential decrease from emitter to collector predicted by earlier studies.

IEEE Transactions on Electron Devices
Department of Electronics

Winterton, S.S., Searles, S., Peters, C.J., Tarr, N.G, & Pulfrey, D.L. (1996). Distribution of base dopant for transit time minimization in a bipolar transistor. IEEE Transactions on Electron Devices, 43(1), 170–172.