Graphene Nanoribbon Tunnel Field-Effect Transistor via Segmented Edge Saturation

Abstract

In this paper, segmented edge saturation (SES) is proposed as a novel method to design high-performance tunnel FETs (TFETs) using smooth graphene nanoribbon (GNR). When the edges of a smooth GNR are saturated by different elements in its different segments, the energy gaps ( ${E}_{g})$ of these segments can be tuned. Therefore, the tunneling and blocking effects are achieved simultaneously by reducing and enlarging the ${E}_{g}$ of GNR in its specific regions. Both high on-to-off current ( ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}})$ ratio and large ${I}_{ \mathrm{\scriptscriptstyle ON}}$ are obtained. Simulation results show that the $\mathrm {I}_{ \mathrm{\scriptscriptstyle OFF}}$ of the SES GNR TFET is below $1 \times 10^{-4} ~\mu \text{A}/\mu \text{m}$ and the ${I}_{{ \mathrm{\scriptscriptstyle ON}}}$ reaches 2000 $\mu \text{A}/\mu \text{m}$ at 0.4-V supply voltage. Detailed transport mechanisms of this TFET are investigated in comparisons with its uniform saturation counterparts. Dynamic performance and scaling ability analyzes are also carried out. The largest intrinsic delay and switching energy are only 0.17 ps and 0.09 fJ/ $\mu \text{m}$ . Meanwhile, it can maintain high ${I}_{{ \mathrm{\scriptscriptstyle ON}}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratios when the channel length is scaled down to several nanometers. The discussions on GNR edge roughness suggest that the roughness should be avoided for better ${I}_{ \mathrm{\scriptscriptstyle ON}}$ behaviors. The good performance of the TFET highlights the capabilities of SES in the developments of GNR tunnel devices.