An analytical model for space-charge region capacitance based on practicaldoping profiles under any bias conditions

An analytical model is presented For quasi-static capacitance of the space- charge region in a p-n junction. The model is valid for realistic junction doping profiles under any bias conditions. It consists of local models in t hree bias regions. For the high-reverse bias region, a novel analytical mod el is derived. For the moderate-bias region, an empirical model commonly us ed in SPICE is adopted. Finally, for the high-forward bias region, the junc tion profiles are approximated by linearly-graded junctions. Existing analy tical models are then modified appropriately to characterize both high-inje ction and heavy-doping effects for advanced bipolar transistors. Compared t o previously developed analytical models or existing empirical models, as w ell as numerical simulation results, the analytical model presented here sh ows an improved accuracy and therefore provides a better tool For both devi ce and circuit simulations. (C) 2001 Elsevier Science Ltd. All rights reser ved.