Van der Waals Photodetector with an Integrated WS₂ Light-Harvesting Antenna

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Graphene photodetectors show promise but require enhanced responsivity.
• Heterostructures with 2D materials, nanoparticles, or quantum dots can improve performance.
• Transition metal dichalcogenides (TMDs) offer unique electronic and optical properties.

Purpose of the Study:

• To investigate the enhancement of a Graphene/MoSe2/Graphene photodetector's photoresponse.
• To explore the role of an external tungsten disulfide (WS2) bilayer as a light-harvesting antenna.
• To understand the mechanism behind the observed responsivity enhancement.

Main Methods:

• Fabrication of a Graphene/MoSe2/Graphene photodetector.
• Integration of an external WS2 bilayer positioned outside the electronic pathway.
• Characterization of the photodetector's photoresponse with and without the WS2 bilayer.

Main Results:

• The photodetector with the external WS2 bilayer exhibited a responsivity enhancement of up to 18 times.
• The WS2 bilayer acted as an optical antenna, transferring energy to the graphene and MoSe2 layers.
• No direct contribution of photoexcited carriers from the WS2 bilayer was observed.

Conclusions:

• Harnessing the excitonic properties of TMDs like WS2 as optical antennas is a viable strategy for enhancing photodetection.
• Energy transfer mechanisms can significantly boost the performance of photodetectors without direct carrier contribution.
• This work introduces a new paradigm for designing high-responsivity photodetectors.