The effect of extrinsic base encroachment on the switch-on transient of advanced narrow-emitter bipolar transistors

A detailed two-dimensional numerical simulations study on the switch-on transient of advanced narrow-emitter bipolar transistors is presented. Particular emphasis is placed on the effect of the 'link-up' region between the extrinsic and intrinsic bases. It is shown that, due to the nonuniform current distribution during the switch-on transient, the encroachment of the extrinsic base into the intrinsic base area causes much more severe degradation in the switching speed of the device than those predicted by DC or quasi-static AC analyses. The design considerations and scaling implications imposed by this transient phenomenon are presented.<
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