Emergence of Quantum Tunneling in Ambipolar Black Phosphorus Multilayers without Heterojunctions

Abstract

Negative differential resistance (NDR) is an exotic quantum tunneling phenomenon that is exhibited in narrow p-n junctions with heavy doping concentrations. However, the presence of multiple heterojunctions in a conventional tunneling device often hampers the observance of NDR and a deep understanding of its origin, particularly in 2D van der Waals heterojunctions. Herein, the emergence of quantum tunneling at the charge neutrality point (V-CNP) in ambipolar multilayered black phosphorus (BP) transistors without heterojunctions is reported. The nearly identical electron and hole carrier densities at V-CNP in the presence of a drain bias (V-D) result in a lateral p-i-n configuration inside the BP multilayers similar to that in a tunneling field-effect transistor. The variation of the local carrier density profile and tunneling barrier with V-D at V-CNP drives a sharp enhancement of the activation energy and local resistance, which consequently allows to observe band-to-band tunneling at up to 340 K. The enhancement of the local doping profile along the BP channel and the NDR behavior in the fabricated reconfigurable top-gate BP device with an h-BN top-dielectric provide further evidence for the origin of NDR in 2D ambipolar materials.