A compact physical expression for the static drain current in heterojunction barrier CNTFETs

Abstract

A physics based compact expression for the static drain current in carbon nanotube field-effect transistors (CNTFETs) is presented, which takes into account the impact of heterojunction barriers at the source and drain end of the channel. The new formulation is based on a closed-form solution of the Landauer equation using a Gaussian-like surrogate function for its energy dependent integrand. The model also includes a smooth transition from thermionic emission based transport in the subthreshold region to tunneling dominated transport in the above-threshold regime. The formulation has been verified for both ballistic and scattering dominated carrier transport in the channel based on data obtained from device simulation of a unit cell structure and measurements of fabricated multi-tube high-frequency (HF) CNTFETs. Including the heterojunction barriers enables to capture the different curve shapes of the device characteristics and their differences in linearity compared to devices with ohmic contacts.