Negative differential resistance with high peak-to-valley ratio via subband resonant tunneling of Γ-valley carriers in WSe₂/h-BN/WSe₂ junctions

Resonant tunneling diodes (RTDs) exhibit negative differential resistance (NDR) in current-voltage characteristics, which is important in various device applications including high-frequency and logic circuits. In this study, we explore a range of WSe₂/h-BN/WSe₂ RTD devices by varying the number of layers of WSe₂, and observe the highest peak-to-valley ratio (PVR) values of 63.6 at 2 K and 16.2 at 300 K with source 3-layer (3L) WSe₂ and drain 1-layer (1L) WSe₂. These PVR values are the highest ever reported for RTDs based on two-dimensional (2D) materials. Traditionally, RTDs were realized in III-V semiconductor superlattices, but high-performance RTDs based on 2D materials have been long awaited. Our findings highlight two key conditions for achieving high PVR: 1) resonant tunneling should occur between the Γ-point bands of the source and drain WSe₂, and 2) the Γ-point bands contributing to the resonant tunneling should be energetically separated from the other bands. These insights mark a significant step towards surpassing the performance of III-V semiconductor RTDs using 2D materials.