MoS₂/Si Heterojunction with Vertically Standing Layered Structure for Ultrafast, High‐Detectivity, Self‐Driven Visible–Near Infrared Photodetectors

TLDR

Molybdenum disulfide (MoS₂) is a promising layered material, yet its optoelectronic applications are limited by poor p–n junction quality, low light absorption in mono/multilayers, and challenges in large‑scale monolayer growth. The study demonstrates that vertically standing MoS₂ films can be deposited on silicon via scalable sputtering to form heterojunction photodetectors. The vertically standing MoS₂ layers are deposited on silicon by sputtering, creating perpendicular molecular layers that provide rapid pathways for photo‑generated carrier separation and transport. The resulting MoS₂/Si heterojunction photodetectors exhibit broadband sensitivity from visible to near‑infrared, an ultrahigh detectivity of ~10¹³ Jones, a response time of ~3 µs, outperforming mono/multilayer MoS₂ devices, and remain stable in air for a month.

Abstract

As an interesting layered material, molybdenum disulfide (MoS 2 ) has been extensively studied in recent years due to its exciting properties. However, the applications of MoS 2 in optoelectronic devices are impeded by the lack of high‐quality p–n junction, low light absorption for mono‐/multilayers, and the difficulty for large‐scale monolayer growth. Here, it is demonstrated that MoS 2 films with vertically standing layered structure can be deposited on silicon substrate with a scalable sputtering method, forming the heterojunction‐type photodetectors. Molecular layers of the MoS 2 films are perpendicular to the substrate, offering high‐speed paths for the separation and transportation of photo‐generated carriers. Owing to the strong light absorption of the relatively thick MoS 2 film and the unique vertically standing layered structure, MoS 2 /Si heterojunction photodetectors with unprecedented performance are actualized. The self‐driven MoS 2 /Si heterojunction photodetector is sensitive to a broadband wavelength from visible light to near‐infrared light, showing an extremely high detectivity up to ≈10 13 Jones (Jones = cm Hz 1/2 W −1 ), and an ultrafast response speed of ≈3 μs. The performance is significantly better than the photodetectors based on mono‐/multilayer MoS 2 nanosheets. Additionally, the MoS 2 /Si photodetectors exhibit excellent stability in air for a month. This work unveils the great potential of MoS 2 /Si heterojunction for optoelectronic applications.