Enhanced performance of a photodetector based on a graphene/CVD-grown dendritic ReS2/Ta2O5 vertical heterojunction

Abstract

To date, many photodetectors exploiting the unique physical properties of transition metal dichalcogenides (TMDs) have been reported. While it is relatively simple to make a new device, optimizing the device's structure and its film morphology to reach its full potential in performance is quite a challenge. In addition, the bulk of the work on TMDs has been conducted using mechanically exfoliated flakes (<1 mm²) with no possibility of large-scale integrations. In this work, the performance of a photodetector is greatly increased by using several distinctive approaches. First, a flower-like ReS₂ film is synthesized to maximize the light absorption surface area for enhanced light absorption and sensing capability. Second, a metal–insulator–semiconductor (MIS) contact layer is employed to reduce the Schottky barrier and lower the contact resistance. Third, the carrier transport is facilitated by utilizing a high mobility graphene layer, which also reduced the work function differences. Last, we structure the device into a vertical heterostructure to minimize the carrier transport distance. The resulting photodetector composed of a graphene/ReS₂/Ta₂O₅ heterojunction exhibited one of the highest photoresponsivities (11.43 A W⁻¹) among devices fabricated with synthesized large-area films. The large area (>1 cm²), nearly transparent device stack can also be readily fabricated on an arbitrary substrate at low temperature (<110 °C) for versatile integration with other electronic platforms.