Solvent-Based Soft-Patterning of Graphene Lateral Heterostructures for Broadband High-Speed Metal-Semiconductor-Metal Photodetectors

Solvents are essential in synthesis, transfer, and device fabrication of 2D materials and their functionalized forms. Controllable tuning of the structure and properties of these materials using common solvents can pave new and exciting pathways to fabricate high-performance devices. However, this is yet to be materialized as solvent effects on 2D materials are far from well understood. Using fluorine functionalized chemical vapor deposited graphene (FG) as an example, and in contrast to traditional "hard-patterning" method of plasma etching, the authors demonstrate a solvent-based "softpatterning" strategy to enable its selective defluorination for the fabrication of graphene-FG lateral heterostructures with resolution down to 50 nm. In this strategy, the oxygen plasma etching process of patterning after graphene transfer is avoided and high quality surfaces are preserved through a physically continuous atomically thin sheet, which is critical for high performance photodetection, especially in the high-speed domain. The fabricated lateral graphene heterostructures are further employed to demonstrate a high speed metal-semiconductor- metal photodetector (< 10 ns response time), with a broadband response from deep-UV (200 nm) to near-infrared (1100 nm) range. Thanks to the high quality surface with much less defects due to the "soft-patterning" strategy, the authors achieve a high deep-UV region photoresponsivity as well as the ultrafast time response. The strategy offers a unique and scalable method to realize continuous 2D lateral heterostructures and underscores the significance of inspiring future designs for high speed optoelectronic devices.