Analysis of subthreshold carrier transport for ultimate DGMOSFET

A novel transport model for the subthreshold mode of double-gate MOSFETs (DGMOSFETs) is proposed in this paper. The model enables the analysis of short-channel effects (SCEs) such as the subthreshold swing (SS), the threshold-voltage rolloff, and the drain-induced barrier lowering. The proposed model includes the effects of thermionic emission and the quantum tunneling of carriers through the source-drain barrier. An approximative solution of the two-dimensional Poisson equation is used for the distribution of the electric potential, and the Wentzel-Kramers-Brillouin approximation is used for the tunneling probability. The model is verified by comparing the SS with numerical simulations. The new model is used to investigate the subthreshold characteristics of a DGMOSFET having the gate length in the nanometer range with an ultrathin gate oxide and channel thickness. The SCEs degrade the subthreshold characteristics of DGMOSFETs when the gate length is reduced below 10 nm, and any design in the sub-10-nm-regime should include the effects of quantum tunneling.