Abstract: In recent years, phototransistors based on two-dimensional semiconductors like transition metal di-chalcogenides including MoS₂ have been studied extensively. Although the phototransistor based on monolayer MoS₂ exhibits a high responsivity, its low carrier mobility also limits the response time of the photodetector to order of seconds. The stacking of two-dimensional semiconductors can form uniform van der Waals heterostructures with low trap defect states, and this is an effective way to improve the performance of two-dimensional photodetectors. In this work, MoS₂/WSe₂ vertical heterostructures were constructed via mechanical exfoliation and transferring method. The strong space charge region originating from the heterojunction can effectively separate the photo-generated carriers, therefore, the as-fabricated photodetectors have good photoelectric detection ability in self-powered mode. The responsivity and detectivity reach 2.12×10³ A/W and 2.33×10¹¹ Jones, respectively. Meanwhile, the response time of the heterojunction device greatly reduces to 40 ms. Such two dimensional heterojunction devices possess the advantages of simple fabrication method and good performance, and has a broad application prospect in the field of optoelectronics.

Key words: MoS₂/WSe₂, pn junction, mechanical stripping transfer method, two dimensional van der Waals heterostructure, photodetector, transition metal di-chalcogenide