Robust Deposition of Sub-Millimeter WSe2 Drive Ultrasensitive Gate-Tunable 2D Material Photodetectors

2D semiconductors are regarded as the potential channel materials for high-performance integrated optoelectronics. However, the absence of an effective photoconductive gain mechanism and the adverse effects from traditional SiO 2 substrate prevent the further breakthrough of the photosensitivity of 2D semiconductors-based photodetectors. Here, an ingenious out-of-plane heterostructure is proposed for boosting the photosensitivity. Sub-millimeter scale (>700 µm) tri-layer WSe 2 with high quality and uniformity is robustly deposited and integrated with 2D photosensitive channels for gate-tunable photodetection. The WSe 2 with naturally passivated surface can not only serve as a substrate passivation layer to mitigate the detrimental substrate effects, but also introduces vertical built-in fields, which efficiently separates the photogenerated carriers and produces high photoconductive gain. Under gate voltage modulation, the proposed InSe photodetector exhibits a series of excellent performances, including responsivity of 112 A W −1 , detectivity of 8.6 × 10 12 Jones, light on/off ratio of 1.3 × 10 4 and rise/decay time of 29.1/15.3 ms. More inspiringly, this heterostructure scheme is universally applicable to 2D WS 2 photodetector and also significantly improves its photosensitivity, demonstrating broad applicability. This research will provide helpful guidance for the design and optimization of customizable optoelectronic devices based on 2D semiconductors.