Monte Carlo simulation of non-equilibrium transport in ultra-thin base Si bipolar transistors

Abstract

Ultra-thin base ( ::; 50 nm) Si n-p-n and p-n-p bipolar transistors were simulated by a two-dimensional, self consistent Monte Carlo program with both electron and hole transport models. The results reveal that two non equilibrium carrier transport effects, velocity overshoot at the base-collector junction and quasi-ballistic transport through the neutral base region, play important roles in shaping the electrical characteristics of these scaled bipolar devices. For such thin base devices, the collector transit time, instead of the base transit time, becomes the major limitation on the device performance. Furthermore, the base transit time of these devices is predicted to be linearly dependent on the neutral base thickness.