Epitaxial growth of wafer-scale molybdenum disulfide/graphene heterostructures by metal−organic vapor-phase epitaxy and their application in photodetectors

Van der Waals heterostructures have attracted increasing interest, owing to the combined benefits of their constituents. These hybrid nanostructures can be realized via epitaxial growth, which offers a promising approach for the controlled synthesis of the desired crystal phase and the interface between van der Waals layers. Here, the epitaxial growth of a continuous molybdenum disulfide (MoS₂) film on large-area graphene, which was directly grown on a sapphire substrate, is reported. Interestingly, the grain size of MoS₂ grown on graphene increases, whereas that of MoS₂ grown on SiO₂ decreases with an increasing amount of hydrogen in the chemical vapor deposition reactor. In addition, to achieve the same quality, MoS₂ grown on graphene requires a much lower growth temperature (400 °C) than that grown on SiO₂ (580 °C). The MoS₂/graphene heterostructure that was epitaxially grown on a transparent platform was investigated to explore its photosensing properties and was found to exhibit inverse photoresponse with highly uniform photoresponsivity in the photodetector pixels fabricated across a full wafer. The MoS₂/graphene heterostructure exhibited ultrahigh photoresponsivity (4.3 × 10⁴ A W⁻¹) upon exposure to visible light of a wide range of wavelengths, confirming the growth of a high-quality MoS₂/graphene heterostructure with a clean interface.