Room-Temperature Graphene-Nanoribbon Tunneling Field-Effect Transistors

Wan Sik Hwang,Gerhard Klimeck,Debdeep Jena,Pei Zhao,Rusen Yan,Alan Seabaugh,Huili Grace Xing,Susan K Fullerton-Shirey,Sung Geun Kim

doi:10.1038/s41699-019-0127-1

Abstract

Controlled, tunable, and reversible negative-differential resistance (NDR) is observed in lithographically defined, atomically thin semiconducting graphene nanoribbon (GNR)-gated Esaki diode transistors at room temperature. Sub-10 nm-wide GNRs patterned by electron-beam lithography exhibit semiconducting energy bandgaps of ~0.2 eV extracted by electrical conductance spectroscopy measurements, indicating an atomically thin realization of the electronic properties of conventional 3D narrow-bandgap semiconductors such as InSb. A p–n junction is then formed in the GNR channel by electrostatic doping using graphene side gates, boosted by ions in a solid polymer electrolyte. Transistor characteristics of this gated GNR p–n junction exhibit reproducible and reversible NDR due to interband tunneling of carriers. All essential experimentally observed features are explained by an analytical model and are corroborated by a numerical atomistic simulation. The observation of tunable NDR in GNRs is conclusive proof of the existence of a lithographically defined bandgap and the thinnest possible realization of an Esaki diode. It paves the way for the thinnest scalable manifestation of low-power tunneling field-effect transistors (TFETs).

Highlights

The single-atom thickness of a two-dimensional (2D) sheet of graphene represents the ultimate limit of how thin one can make an electronically active material.[1,2,3] At present, there is no known way to scale a three-dimensional (3D) semiconductor to such a thickness
In a recent work,[32,33] we experimentally showed that lithographically defined atomically thin, ~10 nm-wide graphene nanoribbon (GNR)-FETs could mimic the electronic behavior of InSb nanowire FETs34 in
As the transistor size is scaled, the energy bandgaps of 3D tunneling junctions increase due to quantum confinement,[4] exponentially reducing the on-state tunneling current. This necessitates the use of intrinsically reduced dimensional 2D or one-dimensional (1D) semiconductor materials for scaled tunneling field-effect transistors (TFETs)

Summary

Introduction

The single-atom thickness of a two-dimensional (2D) sheet of graphene represents the ultimate limit of how thin one can make an electronically active material.[1,2,3] At present, there is no known way to scale a three-dimensional (3D) semiconductor to such a thickness. The source and drain contacts to the GNR are made to zero-gap wide 2D graphene regions.[32,33] Figure 1b shows the measured temperature-dependent transfer characteristics and Fig. 1c shows the conductance spectrum measured at 4 K without side-gate bias for the “control” GNR-FET.

Results

Conclusion