Two-dimensional layered semiconductors present a promising material platform for band-to-band-tunneling devices given their homogeneous band edge steepness due to their atomically flat thickness. Here, we experimentally demonstrate interlayer band-to-band tunneling in vertical MoS2/WSe2 van der Waals (vdW) heterostructures using a dual-gate device architecture. The electric potential and carrier concentration of MoS2 and WSe2 layers are independently controlled by the two symmetric gates. The same device can be gate modulated to behave as either an Esaki diode with negative differential resistance, a backward diode with large reverse bias tunneling current, or a forward rectifying diode with low reverse bias current. Notably, a high gate coupling efficiency of ∼80% is obtained for tuning the interlayer band alignments, arising from weak electrostatic screening by the atomically thin layers. This work presents an advance in the fundamental understanding of the interlayer coupling and electron tunneling in semiconductor vdW heterostructures with important implications toward the design of atomically thin tunnel transistors.

We demonstrate field-effect transistors using heterogeneously stacked two-dimensional materials for all of the components, including the semiconductor, insulator, and metal layers. Specifically, MoS2 is used as the active channel material, hexagonal-BN as the top-gate dielectric, and graphene as the source/drain and the top-gate contacts. This transistor exhibits n-type behavior with an ON/OFF current ratio of >10(6), and an electron mobility of ∼33 cm(2)/V·s. Uniquely, the mobility does not degrade at high gate voltages, presenting an important advantage over conventional Si transistors where enhanced surface roughness scattering severely reduces carrier mobilities at high gate-fields. A WSe2-MoS2 diode with graphene contacts is also demonstrated. The diode exhibits excellent rectification behavior and a low reverse bias current, suggesting high quality interfaces between the stacked layers. In this work, all interfaces are based on van der Waals bonding, presenting a unique device architecture where crystalline, layered materials with atomically uniform thicknesses are stacked on demand, without the lattice parameter constraints. The results demonstrate the promise of using an all-layered material system for future electronic applications.