Resonant tunneling in ReSe₂/h-BN/ReSe₂ van der Waals heterostructures

Multi-layer WSe₂ is gaining attention as a drain/source material in resonant tunneling diodes (RTDs) owing to the notable negative differential resistance (NDR) caused by the hole tunneling at the valence band (VB)-Γ-subbands. In this study, we present the conduction band (CB)-Γ driven RTD using ReSe₂, a type of transition metal dichalcogenides (TMDs) whose CB minimum is near the Γ-point. We perform resonant tunneling measurements for 2L-ReSe₂/h-BN/2L-ReSe₂ van der Waals (vdW) heterostructures and observe electron tunneling at the CB-Γ-point when the ReSe₂ is modulated to N-type through positive gate voltage. As the interlayer bias (V_int) increases, two peaks appear in the I-V_int curve followed by NDR, with the peak-to-valley current ratio (PVR) being 4.1 at 30 K. The spacing between the two peaks is ~0.6 V, corresponding to the energy difference between the 1^st and 2^nd CB-Γ-points in the ReSe₂ band diagram derived by DFT calculations. Results with different temperatures and layer numbers are also discussed. Therefore, we demonstrate that ReSe₂ works as an N-type drain/source material in RTDs through the resonant tunneling at CB-Γ-points. These new findings pave the way for further advanced vdW-RTDs with larger PVR.