Negative Differential Resistance Device with High Peak-to-Valley Ratio Realized by Subband Resonant Tunneling of Γ-Valley Carriers in WSe/-BN/WSe Junctions.

Resonant tunneling diodes (RTDs) are a core technology in III-V semiconductor devices. The realization of high-performance RTD using two-dimensional (2D) materials has been long awaited, but it has yet to be accomplished. To this end, we investigate a range of WSe/-BN/WSe RTD devices by varying the number of layers of source and drain WSe. The highest peak-to-valley ratio (PVR) is demonstrated in the three-layer (3L) WSe/-BN/1-layer (1L) WSe structure. The observed PVR values of 63.6 at 2 K and 16.2 at 300 K are the highest among the 2D material-based RTDs reported to date. Our results indicate the two key conditions to achieve high PVR: (1) resonant tunneling should occur between the Γ-point bands of the source and drain electrodes, and (2) the Γ-point bands contributing to the resonant tunneling should be energetically separated from the other bands. Our results provide an important step to outperform III-V semiconductor RTDs with 2D material-based RTDs.