Analysis of subthreshold swing in multichannel tunneling carbon nanotube field effect transistor (MT-CNTFET)

Abstract

Tunnel Field Effect Transistor (TFET) based on Band-to-Band tunneling mechanism is a revolutionary device technology that has a very strong potential to break the thermodynamic barrier of conventional FETs and provide a very steep subthreshold slope. However, TFETs in general suffer from low on-state current (I ON ). We propose a new TFET structure to increase the drain-to-source current of the tunneling device. The design is based on single-walled carbon nanotubes (SWCNTs). The idea is to provide multiple SWCNTs as tunneling path. We have demonstrated the concept with three SWCNTs. By having three tunneling paths in a single device higher ON current can be achieved while keeping the subthreshold swing lower than 60mV/decade. In this study, the diameter of the tubes and the gate oxide thickness are adjusted to obtain a higher I on and steeper subthreshold slope.

A comprehensive analytical study of electrical properties of carbon nanotube field‐effect transistor for future nanotechnology

“…The tunneling current increases exponentially with increase in tube's diameter . As mentioned by Azzedin D Es‐Sakhi et al, larger CNT diameter leads to larger leakage current, whereas off‐state current decreases as the bandgap decreases. Because the bandgap of CNT material is inversely proportional to the diameter of the tube, SS increases at large diameter as shown in Figure .…”

“…At low V gs , the current in the device is dominated by the BTBT (band-to-band tunneling) current 14,23 and BTBT devices have the potential to offer a steeper slope at room temperature. 24 It is also observed that as V gs increases, the band bends and the tunneling probability increase. 25 The finding of Figure 2 reflects that one can utilize the gate-controlled tunneling to achieve SS value lower than 60 mV/decade at room temperature.…”

“…[23] at high V gs , the source‐channel barrier decreases linearly and thermionic mechanism dominates, which results in larger tunneling current and hence degrades the SS. At low V gs , the current in the device is dominated by the BTBT (band‐to‐band tunneling) current and BTBT devices have the potential to offer a steeper slope at room temperature . It is also observed that as V gs increases, the band bends and the tunneling probability increase .…”