Negative differential resistance in ReSe2/ <i>h</i> -BN/ReSe2 van der Waals tunnel junction

Van der Waals (vdW) heterostructures composed of two-dimensional (2D) materials offer atomically sharp interfaces and atomic-level control over layer thickness, making them highly suitable for quantum well (QW) applications. Such vdW QWs allow the integration of a wide variety of 2D materials owing to the absence of lattice-matching constraints in vdW interfaces, offering the potential to uncover advanced electronic and optoelectronic functionalities. In this study, we investigated rhenium diselenide (ReSe2) as a promising candidate for a vdW QW material. A ReSe2/h-BN/ReSe2 tunnel junction was constructed using monolayer-to-trilayer-thick ReSe2 as the QW layer and few-layer-thick h-BN as the tunnel barrier. By tuning the carrier polarity of the ReSe2 layers using gate voltages, the electron or hole tunneling characteristics between the QW layers were investigated. For both polarities, the current–voltage characteristics exhibited multiple peaks, which were attributed to tunneling from the source-side ReSe2 into the Γ-point bands of the drain-side ReSe2. In the case of electron tunneling, distinct peaks accompanied by significant negative differential resistance were observed, clearly indicating energy- and momentum-conserved resonant tunneling between the Γ-point bands of the source and drain ReSe2. We found that the bilayer ReSe2 device exhibited a maximum peak-to-valley current ratio (PVR) of 4.1, which is a noticeably high PVR value among vdW-based resonant electron tunneling devices. These results highlight the potential of ReSe2 as an n-type vdW QW material and pave the way for future developments of quantum electronic devices based on 2D material heterostructures.