▎ 摘　　要

Black phosphorus (BP) as a promising candidate for mid-wave infrared (MWIR) detection has attracted much attention. However, the high-speed photoresponse at the MWIR is yet to be a challenge. In this paper, we report a BP-graphene heterostructure photodetector with fast photoresponse at MWIR range using molybdenum electrode as a contact to realizing a low Schottky barrier. The device exhibits a fast photoresponse in a broad-spectrum range from visible to MWIR (0.67-4.2 mu m). A high photovoltaic responsivity up to 183 mA W-1 and EQE up to 35.6% were realized at the visible range of 0.637 mu m light and respectively 7.9 mA W-1 and 0.31% at MWIR 3098 nm. The specific detectivity D* = 6.69 x 10(8) Jones is obtained at 1 mV bias under the illumination of the MWIR 4.25 mu m in the ambient condition. Our work may open a new way to realizing fast MWIR photoresponse at the low light level.