Strong electrically tunable MoTe₂/graphene van der Waals heterostructures for high-performance electronic and optoelectronic devices

MoTe₂ is an emerging two-dimensional layered material showing ambipolar/p-type conductivity, which makes it an important supplement to n-type two-dimensional layered material like MoS₂. However, the properties based on its van der Waals heterostructures have been rarely studied. Here, taking advantage of the strong Fermi level tunability of monolayer graphene (G) and the feature of van der Waals interfaces that is free from Fermi level pinning effect, we fabricate G/MoTe₂/G van der Waals heterostructures and systematically study the electronic and optoelectronic properties. We demonstrate the G/MoTe₂/G FETs with low Schottky barriers for both holes (55.09 meV) and electrons (122.37 meV). Moreover, the G/MoTe₂/G phototransistors show high photoresponse performances with on/off ratio, responsivity, and detectivity of ∼10⁵, 87 A/W, and 10¹² Jones, respectively. Finally, we find the response time of the phototransistors is effectively tunable and a mechanism therein is proposed to explain our observation. This work provides an alternative choice of contact for high-performance devices based on p-type and ambipolar two-dimensional layered materials.