Emergence of Quantum Tunneling in Ambipolar Black Phosphorus Multilayers without Heterojunctions

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 (VCNP) in ambipolar multilayered black phosphorus (BP) transistors without heterojunctions is reported. The nearly identical electron and hole carrier densities at VCNP in the presence of a drain bias (VD) 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 VD at VCNP 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. Quantum tunneling in ambipolar multilayered black phosphorus (BP) transistors at the charge neutrality point voltage (VCNP) is demonstrated without heterojunctions. Under bipolar conduction near the VCNP, a p‐i‐n configuration is successfully obtained along the BP channel and negative differential resistance (NDR) is realized via band‐to‐band tunneling. The fabricated reconfigurable top‐gate BP device provides further evidence for the origin of NDR.