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 (ΔV) exhibit a high cut off frequency and low power consumption efficiency, which is significant for fabricating high-performance oscillators. However, achieving an ultralow ΔV 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 ΔV 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.