Black Phosphorus Nanoflakes Vertically Stacked on MoS₂ Nanoflakes as Heterostructures for Photodetection

Heterostructures of two-dimensional (2D) materials are being actively explored for a plethora of applications because of their ability to form stacked layers that provide access to a combination of favorable electronic and optical properties. One such strategy is combining p- and n-type 2D materials to create versatile p–n junctions to modulate electrical and optoelectronic behaviors based on the type of band alignment between the constituent materials. In this context, black phosphorus (BP) and molybdenum disulfide (MoS2) offer promising prospects for optoelectronics. However, studies on the photoresponsivity (R), specific detectivity (D*), and external quantum efficiency (EQE) in both forward and reverse operating modes of a BP-MoS2 diode across a wide-wavelength spectrum have not been reported. Herein, we demonstrate photodetection capabilities of a heterostructure formed from layers of BP and MoS2 over a UV (280 nm)–vis (660 nm) wavelength range. The heterojunction which can be electrically tuned by means of a gate voltage achieves a rectification ratio of 47 while operating at a relatively low electrical bias. High room-temperature responsivity and detectivity values are obtained along with an EQE of 200%. Overall, the detection spectrum of this heterostructure is wider than each of the constituent materials on their own. This work adds important fundamental knowledge in BP-MoS2 heterostructure research at the nanoscale that will enable more efficient optoelectronic devices.