Observing the semiconducting band-gap alignment of MoS₂ layers of different atomic thicknesses using a MoS₂/SiO₂/Si heterojunction tunnel diode

We demonstrate a tunnel diode composed of a vertical MoS₂/SiO₂/Si heterostructure. A MoS₂ flake consisting four areas of different thicknesses functions as a gate terminal of a silicon field-effect transistor. A thin gate oxide allows tunneling current to flow between the n-type MoS₂ layers and p-type Si channel. The tunneling-current characteristics show multiple negative differential resistance features, which we interpret as an indication of different conduction-band alignments of the MoS₂ layers of different thicknesses. The presented tunnel device can be also used as a hybrid-heterostructure device combining the advantages of two-dimensional materials with those of silicon transistors.