Bifunctional Semimetal as a Plasmonic Resonator and Ohmic Contact for an Ultrasensitive MoS2 Photodetector

Monolayer transition-metal dichalcogenides (TMDCs) have great potential for realizing high-performance nanoelectronic and optoelectronic devices. However, contact resistance originating from the Fermi-level pinning effect leads to high power consumption and poor photocurrent transport capability in TMDC photodetectors. Moreover, the atomically thin nature of monolayer TMDCs limits their absorption and optoelectronic performance. Here, an all-semimetal plasmonic photodetector that consists of monolayer MoS2 integrated with Bi contact electrodes and Bi plasmonic nanodisks is presented to address these issues. By utilizing Bi as the contact metal, the Fermi-level pinning effect at the metal-semiconductor interface is suppressed, which increases the response speed and reduces the photocurrent loss to contact resistance. Furthermore, the strongly localized electromagnetic field across the interface between Bi plasmonic structures and MoS2 enhances the photon-to-exciton conversion efficiency over 4 times at 600 nm. Photoresponsivity of this all-semimetal MoS2 photodetector shows a 690% enhancement compared to the pristine device with conventional electrodes. In addition, the detectivity of our device reaches 6.40 × 1012 Jones, which is the highest value reported for plasmonic MoS2 photodetectors. This work demonstrates that integrating multifunctional semimetal with TMDCs offers a new approach to realizing high-performance and energy-efficient TMDC optoelectronic devices.