SIMULATION AND MODELING OF TUNNELING CARBON NANOTUBES FIELD EFFECT TRANSISTORS (T-CNFETS)

Abstract

Carbon Nanotube Field Effect Transistors (CNFETs) are a potential candidate to replace conventional MOSFETs. They show high current capabilities due to their 1-D nature and ballistic transport.

In this work we study in detail the operation principals ofMOSFET-like CNFETs and Tunneling-CNFETs. The study is based on using self-consistent quantum mechanical simulator using the Non-Equilibrium Green's Function (NEGF) method where Schrodinger's equation is solved self-consistently with Poisson's equation. The quantum mechanical simulator used in this work is MOSCNT available on [NanoHub]. Slight modifications to the simulator have been made to help in understanding the transistors underlying physics.

T-CNFETs could have a subthreshold swing slope less than the theoretical thermal limit of 60mV/decade. We proved that T-CNFETs can't be used in high power applications because they will have undesired switching performance.

We also propose a novel computational approach to model T-CNFETs based on our understanding of the underlying physics of the transistor operation. The model takes into account the dominant current component, band-to-band tunneling current, as well as thermionic emission and tunneling through the carbon nanotube bandgap. Although the lowest subband carries almost more than 90% of the total current, current in multiple subbands with interband tunneling has been also taken into account.

The advantage of our computational approach is that it reduces the computational time with respect to the more rigorous NEGF formalism. Comparison between the results obtained from the computational model and the NEGF is also presented showing a good agreement in the 1-V characteristics for different carbon nanotube chiralities and asymmetric source/drain doping values.