Gate-Tunable Ultrahigh Photoresponsivity of 2D Heterostructures Based on Few Layer MoS₂ and Solution-Processed rGO

2D materials heterostructures are built by vertical stacking of solution-processed reduced graphene oxide (rGO) film and few-layer MoS₂. The Raman and photoluminescence of the MoS₂/rGO heterostructures show more significant peak shift compared to individual MoS₂ or rGO film. The field-effect transistors (FETs) based on such MoS₂/rGO heterostructures show ambipolar behavior in the dark but n-type behavior under illumination. This phenomenon provides a way to investigate the charge transport in valence band of MoS₂. Due to charge separation caused by built-in potential at MoS₂/rGO interface, the recombination of photoexcited electron–hole pairs is effectively suppressed, leading to high photoresponsivity (≈2.4 × 10⁴ A W⁻¹) and photogain (≈4.7 × 10⁴) of the MoS₂/rGO heterostructures in ambient air with modulation of gate bias and drain–source bias.