Inversion gate capacitance of undoped single-gate and double-gate field-effect transistor geometries in the extreme quantum limit

Abstract

We present first-principle analytical derivations and numerically modeled data to show that the gate capacitance per unit gate area C<inf>G</inf> of extremely thin undoped-channel single-gate and double-gate field-effect transistor geometries in the extreme quantum limit with single-subband occupancy can be written as 1/C<inf>G</inf>=1/C<inf>OX</inf>+N<inf>G</inf>/C<inf>DOS</inf>+N<inf>G</inf>/ηC<inf>WF</inf>, where N<inf>G</inf> is the number of gates, C<inf>OX</inf> is the oxide capacitance per unit area, C<inf>DOS</inf> is the density-of-states capacitance per unit area, C<inf>WF</inf> is the wave function spreading capacitance per unit area, and η is a constant on the order of 1.