Visible to Near-Infrared Photodetector with Novel Optoelectronic Performance Based on Graphene/S-doped InSe Heterostructure on h-BN Substrate

Van der Waals heterostructures of two-dimensional (2D) materials have attracted considerable attention due to the flexibility in designing new functional devices. Despite numerous studies on graphene/2D semiconductors heterostructures, their optoelectronic applications are significantly hindered because of several disadvantages, such as large band gap and chemical instability. In this work, we demonstrate the fabrication of graphene/S-doped InSe heterostructure photodetectors with excellent photoresponse performance, which is attributed to the moderate band gap and band gap engineering by element doping of InSe as well as high carrier mobility of graphene. In particular, the graphene/InSe0.9S0.1 device achieves an ultrahigh photoresponsivity of ~4.9 × 106 A/W at 700 nm and EQE of 8.7 × 108%, and exhibits broadband photodetection (visible to near-infrared). More importantly, in virtue of the interaction between n-type graphene arising from the influence of h-BN as a dielectric layer and S-doped InSe with high work-function, our devices always exhibit positive photocurrent when adjusting the polarity of gate voltage, which is different from that of graphene/2D semiconductor photodetectors reported previously. This work not only provides a promising platform for highly efficient and broadband photodetectors but also sheds light on tuning the optoelectronic performance through band gap engineering and designing novel heterostructures based on various 2D materials.