Polarization engineered all 2D Graphene/Ferroelectric hybrid for persistence-free photoresponse
Graphene-based van der Waals hybrid photodetectors typically work on trap-mediated photogating mechanism, exhibiting high sensitivity, but under-perform in the fast detection of repetitive optical signals. Designing photodetectors that are simultaneously fast and highly sensitive has therefore remained difficult. In this work, we realize both attributes by integrating atomically thin sliding ferroelectrics in the design architecture, thereby uniting semiconducting properties with intrinsic polarization fields capable of efficiently governing interfacial photocarrier dynamics. We report a bilayer graphene-bilayer MoS2 (with MoS2 in a rhombohedrally stacked (3R) configuration) van der Waals photodetector with edge-contacted dual-gated field-effect transistor architecture. The photo-induced modulation in spontaneous out-of-plane polarization of 3R-MoS2 and selective confinement of charge carriers in bilayer graphene under an out-of-plane displacement field results in a tunable persistence-free photoresponse. Here, the photoinduced polarization change in 3R-MoS2 produces an optically controlled gating effect that alters the electrostatic environment of bilayer graphene, resulting in a temperature-independent photoresponse with rapid response times of the order of 10's of milliseconds (limited by the measurement instrument). We demonstrate reproducible detection of optical signals and examine the photon-counting resolution of this structure in high-sensitivity regimes, where we determine its internal quantum efficiency to be 10 percent with minimum detectable photon number of 31 in single shot measurements. This work highlights the functionality of 3R-MoS2 in manipulating the interfacial charge dynamics and establishes the hybrid of graphene and ferroelectric 3R-MoS2 as a promising platform for ultra-sensitive optoelectronic devices.