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 SiO2 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 mu m) tri-layer WSe2 with high quality and uniformity is robustly deposited and integrated with 2D photosensitive channels for gate-tunable photodetection. The WSe2 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 x 10(12) Jones, light on/off ratio of 1.3 x 10(4) and rise/decay time of 29.1/15.3 ms. More inspiringly, this heterostructure scheme is universally applicable to 2D WS2 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.