Room-Temperature Graphene-Nanoribbon Tunneling Field-Effect Transistors

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 similar to 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).