Graphene/In ₂ S ₃ van der Waals Heterostructure for Ultrasensitive Photodetection

As an emerging 2D nonlayered material, natural defective β-In ₂ S ₃ nanosheets have drawn attention because of their unique defective structure and broad optical detection range. Stacking n-type In ₂ S ₃ with other p-type 2D materials can produce an atomically sharp interface with van der Waals interaction, which may lead to high performance in (opto)electronics. In this study, we fabricated a van der Waals heterostructure composed of In ₂ S ₃ and graphene via the dry transfer method. Scanning Kelvin probe force microscopy revealed a significant potential difference at the interface of the heterostructure, thereby endowing it with good diode characteristics. The back-gate field effect transistor based on the graphene/In ₂ S ₃ heterostructure exhibited excellent gate-tunable current-rectifying characteristic with n-type semiconductor behavior. A photodetector based on the graphene/In ₂ S ₃ heterostructure showed excellent response to visible light. Particularly, an ultrahigh responsivity of 795 A/W and an external quantum efficiency of 2440% are recorded under the illumination of 405 nm light and can be further increased to 8570 A/W and 26200% with a positive gate voltage of 60 V. The excellent optical responsive performance is attributed to the synergy of photoconductive and photogating effects. These intriguing results suggest that the graphene/In ₂ S ₃ heterostructure has prospective applications in future electronic and optoelectronic devices.