An Improved Virtual-Source-Based Transport Model for Quasi-Ballistic Transistors—Part I: Capturing Effects of Carrier Degeneracy, Drain-Bias Dependence of Gate Capacitance, and Nonlinear Channel-Access Resistance

In this paper, an improved physics-based virtual-source (VS) model to describe transport in quasi-ballistic transistors is discussed. The model is based on the Landauer scattering theory, and incorporates the effects of: 1) degeneracy on thermal velocity and mean free path of carriers in the channel; 2) drain-bias dependence of gate capacitance and VS charge, including the effects of band nonparabolicity; and 3) nonlinear resistance of the extrinsic device region on gm-degradation at high drain currents in the channel. The improved charge model captures the phenomenon of reduction in VS charge under nonequilibrium transport conditions in a quasi-ballistic transistor.