Negative Differential Resistance with Ultralow Peak-to-Valley Voltage Difference in Td-WTe₂/2H-MoS₂ Heterostructure

Negative differential resistance (NDR) devices with a low peak-to-valley voltage difference (Δ<i>V</i>) exhibit a high cut off frequency and low power consumption efficiency, which is significant for fabricating high-performance oscillators. However, achieving an ultralow Δ<i>V</i> is challenging. In this work, we report the first construction of an NDR device utilizing a van der Waals heterostructure composed of semimetallic Td-WTe₂ and semiconducting 2H-MoS₂. Our findings reveal that the narrow energy region of the decreasing density of states (DOS) above the Fermi level of WTe₂ acts as a narrow band gap, facilitating type-III band alignment with MoS₂ and enabling band-to-band tunneling-based NDR transport. Notably, the NDR device exhibits an ultralow Δ<i>V</i> 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-WTe₂ in NDR transport.