Dominant n-type conduction and fast photoresponse in BP/ MoS 2 heterostructures

In recent years, van der Waals heterojunctions between two-dimensional (2D) materials have garnered significant attention for their unique electronic and optoelectronic properties and have opened avenues for innovative device architectures and applications. Among them, the heterojunction formed by black phosphorus (BP) and molybdenum disulfide (MoS 2 ) stands out as a promising candidate for advanced optoelectronic devices. This study unravels the interplay between BP, MoS 2 , and Cr contacts to explain the electrical behavior of a BP/MoS 2 heterojunction showing rectifying behavior with dominant n-type conduction, and a high ON/OFF current ratio around 10 4 at +/- 20 V. The higher unexpected current observed when applying a negative bias to either MoS 2 or BP side is elucidated by an energy band model incorporating a type II heterojunction at the BP/MoS 2 interface with Cr forming a Schottky contact with MoS 2 and an ohmic contact with BP. The BP/MoS 2 heterojunction shows pronounced photoresponse, linearly dependent on the incident laser power, with a responsivity of 100 mu A/W under white light at 50 mu W incident power. Time -resolved photocurrent measurements reveal a relatively fast response with characteristic rise times less than 200 ms. This work demonstrates that BP/MoS 2 van der Waals heterojunctions have unique electrical and photoresponse characteristics that are promising for advanced optoelectronic applications.