A Core Compact Model for Multiple-Gate Junctionless FETs

Abstract

A core model for multiple-gate junctionless FETs (Mug-JL-FETs) is proposed. The derived charge model is obtained via assumptions of simple potential profile for different types of Mug-JL-FETs. It was found that the linear potential approach is not accurate enough for a double-gate (DG) JL-FET, whereas it was reasonably precise for a DG inversion-mode FET. This discrepancy arises from their different operating mechanisms. Thus, the parabolic potential assumption, which is intuitively close to an actual potential profile in the Mug-FETs, was applied. As a consequence, two different formulas of the charge model in terms of depletion charges, gate capacitance, and capacitance inside the channel were found: one for a tetragonal shape of a cross-sectional channel based on a Cartesian coordinate and the other for a circular shape of a cross-sectional channel based on a cylindrical coordinate. Moreover, the proposed approach was applied for a realistically shaped channel, which is close to elliptic geometry, with a circular profile at the top and bottom parts of the channel and a rectangular profile at the center part of the channel. By applying the decoupling method reported previously, a drain current model, which is extended from the above-mentioned charge model, was also obtained.