Effect of doping profile variation on nanoscale cylindrical gate carbon nanotube field-effect transistor: a computational study using nonequilibrium Green’s function formalism

Abstract

The scaling down of modern devices beyond 15 nm has faced major setbacks as it engendered short channel effects which were seemingly inexorable. One of the solutions proposed was to replace the conventional silicon channel with carbon nanotubes (CNTs), giving rise to the carbon nanotube field-effect transistor (CNTFET). CNTs provide unrivaled electrical and mechanical properties which make them an attractive alternative to silicon for channel materials. In this research work, a cylindrical gate CNTFET model is proposed, and its performance is studied and compared with existing experimental results. The performance of the device due to the variation in the doping profile of the source and drain is studied to realize a device that can manifest superior characteristics compared with existing devices. A model with a non-uniform doping profile is proposed that results in a significant reduction in leakage current. The characteristics upon which the performance is evaluated are the on/off current ratio (I ON/I OFF), subthreshold swing (SS), and threshold voltage. By adjusting various parameters, a device is constructed with I ON/I OFF of 4 × 106, SS of 63 mV dec−1 (approximately), and a threshold voltage of 0.45 V, which performs better than existing devices shown in the literature. All the simulations have been performed by employing the nonequilibrium Green’s function formalism with the self-consistent solution of the Schrödinger and Poisson equations.