| Summary: | This paper studies band-to-band tunneling in the transverse and lateral directions of van der Waals MoS₂/WSe₂ heterojunctions. We observe room-temperature negative differential resistance (NDR) in a heterojunction diode comprised of few-layer WSe₂ stacked on multilayer MoS₂. The presence of NDR is attributed to the lateral band-to-band tunneling at the edge of the MoS₂/WSe₂ heterojunction. The backward tunneling diode shows an average conductance slope of 75 mV/dec with a high curvature coefficient of 62 V-1. Associated with the tunnel-diode characteristics, a positive-to-negative transconductance in the MoS₂/WSe₂ heterojunction transistors is observed. The transition is induced by strong interlayer coupling between the films, which results in charge density and energy-band modulation. The sign change in transconductance is particularly useful for multivalued logic (MVL) circuits, and we therefore propose and demonstrate for the first time an MVL-inverter that shows three levels of logic using one pair of p-type transistors.
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