Graphene p–n Vertical Tunneling Diodes

Abstract

Formation and characterization of graphene p–n junctions are of particular interest because the p–n junctions are used in a wide variety of electronic/photonic systems as building blocks. Graphene p–n junctions have been previously formed by using several techniques, but most of the studies are based on lateral-type p–n junctions, showing no rectification behaviors. Here, we report a new type of graphene p–n junction. We first fabricate and characterize vertical-type graphene p–n junctions with two terminals. One of the most important characteristics of the vertical junctions is the asymmetric rectifying behavior showing an on/off ratio of ∼10³ under bias voltages below ±10 V without gating at higher n doping concentrations, which may be useful for practical device applications. In contrast, at lower n doping concentrations, the p–n junctions are ohmic, consistent with the Klein-tunneling effect. The observed rectification results possibly from the formation of strongly corrugated insulating or semiconducting interlayers between the metallic p- and n-graphene sheets at higher n doping concentrations, which is actually a structure like a metal–insulator–metal or metal–semiconductor–metal tunneling diode. The properties of the diodes are almost invariant even 6 months after fabrication