High-Performance WSe₂ Photodetector Based on a Laser-Induced p-n Junction

Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe₂ p-n junction. The laser-scanned region shows p-type behavior, and the adjacent region is electrically n-doped with a proper gate voltage. The laser-oxidized product WO_x is found to be responsible for this p-type doping. After laser scanning, WSe₂ displays a change from ambipolar to unipolar p-type property. A significant photocurrent emerges at the p-n junction. Therefore, a self-powered WSe₂ photodetector can be fabricated based on this junction, which presents a large photoswitching ratio of 10⁶, a high photoresponsivity of 800 mA W^-1, and a short photoresponse time with long-term stability and reproducibility. Therefore, this selective laser-doping method is prospective in future electronic applications.