Lateral scaling effects on high-current transients in submicrometer bipolar transistors

High-current turn-on and turn-off transients for submicrometer bipolar transistors were studied in detail using two-dimensional numerical computer simulation. It is shown that, when the emitter line width is scaled down from 0.4 to 0.1 mu m, only a little improvement is achieved in the turn-on transient, while the time delay is drastically reduced in the turn-off transient. This is due to the difference between the charge and discharge process for excess holes stored in the peripheral region of the base and the emitter. Emitter current oscillation was observed in the turn-off transient, which is attributed to the complicated change in the discharge path.>