Negative Differential Resistance with Ultralow Peak-to-Valley Voltage Difference in Td-WTe 2 /2H-MoS 2 Heterostructure.

Negative differential resistance (NDR) devices with a low peak-to-valley voltage difference (Δ V ) exhibit a high cut off frequency and low power consumption efficiency, which is significant for fabricating high-performance oscillators. However, achieving an ultralow Δ V is challenging. In this work, we report the first construction of an NDR device utilizing a van der Waals heterostructure composed of semimetallic Td-WTe 2 and semiconducting 2H-MoS 2 . Our findings reveal that the narrow energy region of the decreasing density of states (DOS) above the Fermi level of WTe 2 acts as a narrow band gap, facilitating type-III band alignment with MoS 2 and enabling band-to-band tunneling-based NDR transport. Notably, the NDR device exhibits an ultralow Δ V of approximately 0.01 V, which is at least an order of magnitude lower than previously reported values. This work not only introduces a new approach for NDR device fabrication but also provides new insights into the pivotal role of Td-WTe 2 in NDR transport.