Interplay of charge transfer and disorder in optoelectronic response in Graphene/hBN/MoS2 van der Waals heterostructures

Ahmed, T and Roy, K and Kakkar, S and Pradhan, A and Ghosh, A (2020) Interplay of charge transfer and disorder in optoelectronic response in Graphene/hBN/MoS2 van der Waals heterostructures. In: 2D Materials, 7 (2).

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Abstract

Strong optoelectronic response in the binary van der Waals heterostructures of graphene and transition metal dichalcogenides (TMDCs) is an emerging route towards high-sensitivity light sensing. While the high sensitivity is an effect of photogating of graphene due to inter-layer transfer of photo-excited carriers, the impact of intrinisic defects, such as traps and mid-gap states in the chalcogen layer remain largely unexplored. Here we employ graphene/hBN (hexagonal boron nitride)/MoS2 (molybdenum disulphide) trilayer heterostructures to explore the photogating mechanism, where the hBN layer acts as interfacial barrier to tune the charge transfer timescale. We find two new features in the photoresponse: First, an unexpected positive component in photoconductance upon illumination at short times that preceeds the conventional negative photoconductance due to charge transfer, and second, a strong negative photoresponse at infrared wavelengths (up to 1720 nm) well-below the band gap of single layer MoS2. Detailed time and gate voltage-dependence of the photoconductance indicates optically-driven charging of trap states as possible origin of these observations. The responsivity of the trilayer structure in the infrared regime was found to be extremely large (> 108 A/W at 1550 nm using 20 mV source drain bias at 180 K temperature and � - 30 V back gate voltage). Our experiment demonstrates that interface engineering in the optically sensitive van der Waals heterostructures may cast crucial insight onto both inter- and intra-layer charge reorganization processes in graphene/TMDC heterostructures. © 2020 IOP Publishing Ltd.

Item Type:	Journal Article
Publication:	2D Materials
Publisher:	IOP Publishing Ltd
Additional Information:	Copyright for this article belongs to IOP Publishing Ltd.
Keywords:	Energy gap; Graphene; III-V semiconductors; Layered semiconductors; Molybdenum compounds; Sulfur compounds; Threshold voltage; Transition metals; Van der Waals forces, Hexagonal boron nitride; Infrared wavelengths; Interface engineering; Interfacial barriers; Molybdenum disulphide; Photoexcited carriers; Transition metal dichalcogenides; Trilayer heterostructures, Charge transfer
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering Division of Physical & Mathematical Sciences > Physics
Date Deposited:	09 Apr 2021 06:27
Last Modified:	09 Apr 2021 06:27
URI:	http://eprints.iisc.ac.in/id/eprint/65287

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