Negative Differential\nResistance Device with High\nPeak-to-Valley Ratio Realized by Subband Resonant Tunneling of Γ‑Valley\nCarriers in WSe<sub>2</sub>/<i>h</i>‑BN/WSe<sub>2</sub> Junctions

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