Resonant tunneling in van der Waals triple quantum well device based on WSe₂/h-BN/WSe₂/h-BN/WSe₂ junctions

Few-layer (FL) semiconducting transition metal dichalcogenides (TMDs) exhibit subband structures due to out-of-plane quantum confinement, analogous to quantum wells (QWs). Here, we realize vertical tunneling in a van der Waals triple QW (vdW TQW) structure composed of trilayer (3L) -WSe₂/h-BN/3L-WSe₂/h-BN/3L-WSe₂. In this structure, the three-level subband formed in the 3L WSe₂ functions as a vdW QW, and the few-layer-thick h-BN acts as a tunnel barrier. Applying a bias between the first and third QWs enables control of the resonant tunneling between QWs. The fabricated TQW exhibits five sharp resonant tunneling peaks accompanied by negative differential resistance in its current–voltage characteristics. This is in stark contrast to the double QW structure of 3L-WSe₂/h-BN/3L-WSe₂, which shows only three resonant tunneling peaks. This phenomenon can be attributed to the multiplication of resonant tunneling, originating from the avoided coincidence of resonant tunneling at the first and second tunnel barriers. The realization of vdW multiple QWs demonstrates a significant step toward high-performance oscillators and logic devices based on 2D materials.