An improved virtual-source-based transport model for quasi-ballistic transistors - Part II: Experimental verification

In the first part of this two-part paper, a revised MIT virtual-source (MVS)-based transport model, called MVS-2, is presented. The MVS-2 model captures the essential physics of quasi-ballistic nanotransistors by accounting for the effects of: 1) degeneracy on the thermal velocity and the mean free path of the carriers in the channel; 2) nonequilibrium transport conditions on the gate-channel capacitance; and 3) the conduction band nonparabolicity on the effective mass of the carriers. The formulation of the extrinsic device regions as nonlinear current-dependent resistances allows MVS-2 to describe the degradation in the device transconductance under high drain currents as measured experimentally in InGaAs quantum well HEMT devices. In this paper, we test the accuracy of the MVS-2 model by comparing the model results with the measured $I$-$V$ data of the InGaAs HEMT devices with gate lengths from 30 to 130 nm and Si extremely thin silicon on insulator devices with gate lengths from 30 to 50 nm. We also discuss why at the expense of some physical rigor the basic MVS model can fit more simply the experimental data (except for the degradation in transconductance under high drain currents).