Promoting the Performance of 2D Material Photodetectors by Dielectric Engineering.
Jianting LuZexiang DengQiaojue YeZhaoqiang ZhengJiandong YaoGuowei YangPublished in: Small methods (2021)
Low light absorption and limited carrier lifetime are two limiting factors hampering the further breakthrough of the performance of 2D materials (2DMs)-based photodetectors. This study proposes an ingenious dielectric engineering strategy toward boosting the photosensitivity. Periodic dielectric structures (PDSs), including SiO 2 /h-BN, SiO 2 /Al 2 O 3 , and SiO 2 /SrTiO 3 (STO), are exploited to couple with 2D photosensitive channels (denoted as PDS-2DMs). The responsivity, external quantum efficiency, and detectivity of an optimized SiO 2 /STO (300 nm) -WSe 2 photodetector reach 89081 A W -1 , 2.7 × 10 7 %, and 1.8 × 10 13 Jones, respectively. These performance metrics are orders of magnitude higher than a pristine WSe 2 photodetector, enabling reliable sub-1 pW weak light detection. Based on systematic characterizations and first-principle calculations, such dramatic performance improvement is associated with the promoted direct bandgap transition, reduced exciton binding energy, and PDS-induced periodic intramolecular built-in electric field across the atomically thin channels, which efficiently separates the photoexcited electron-hole pairs. More inspiringly, this strategy is also successfully exploited to 2D WS 2 photodetectors, demonstrating broad applicability. As a whole, this work promises an exceptional avenue to ameliorate 2DM photodetectors and opens up a new horizon "dielectric optoelectronics," simultaneously highlighting the role of dielectric environment during analyzing the fundamentals of 2DM devices.
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