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 ~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).