Approximate Analysis of Cylindrical Ferroelectric Capacitor and Derivation of Drain Current Characteristics in Ferroelectric Gate-All-Around Carbon Nanotube Transistor

Abstract

Drain current vs gate voltage and drain current vs drain voltage characteristics have been derived in a ferroelectric gate-all-around carbon nanotube (CNT) transistor. An approximate analysis to derive the polarization characteristics in a cylindrical ferroelectric capacitor is first presented. It has been found that the characteristics can be approximated by those of a parallel-plate capacitor having the same area as the inner electrode of the cylindrical capacitor and the same thickness as the ferroelectric cylinder. Then, the drain current characteristics of the ferroelectric gate-all-around CNT transistor are derived by combining the analysis on the cylindrical capacitor and the ballistic transport theory on CNT transistors. The gate structure is assumed to be such that CNTs with diameters of 1 and 2 nm are surrounded with a 5-nm-thick poly(vinyliden fluoride–trifluoroethylene) [P(VDF–TrFE)] film. It has been found that, in this structure, the CNT transistor can operate as a memory transistor with an appropriate voltage margin.