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Low-resistance metal contacts to encapsulated semiconductor monolayers with long transfer length

Nature Electronics volume 5, pages 579–585 (2022)Cite this article

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Abstract

Two-dimensional semiconductors such as transition metal dichalcogenides are of potential use in electronic and optoelectronic devices due to their high mobility, direct optical bandgap and mechanical flexibility. These semiconductors are often encapsulated with hexagonal boron nitride to minimize extrinsic disorder and improve performance, but it is challenging to make high-quality contacts to encapsulated high-purity monolayers. Here we show that metal contacts embedded within hexagonal boron nitride can be transferred onto clean transition metal dichalcogenide monolayers, in an approach that reduces doping, strain and interfacial roughness compared with evaporated metal contacts. Contacts to encapsulated ultraclean tungsten diselenide monolayers created using this technique exhibit a room-temperature contact resistance of around 5 kΩ μm, and provide transistors with zero hysteresis and room-temperature mobility of 655 cm2 V−1 s−1. The contacts also exhibit a transfer length of 1 μm, which is several orders of magnitude larger than the channel thickness.

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Fig. 1: Assembly and characterization of 3D metal electrodes–hBN/monolayer TMDs/hBN heterostructure.
Fig. 2: Room-temperature electrical performance of monolayer WSe2 FET.
Fig. 3: Characterization of contact resistance and mobility.
Fig. 4: Probing the mechanism underlying the low contact resistance.
Fig. 5: Comparison of contact characteristics.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Change history

  • 14 September 2022

    In the version of this article initially published, there was a conversion error in Fig. 1b which has now been restored in the HTML and PDF versions of the article.

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Acknowledgements

This work was primarily supported by the NSF MRSEC program at Columbia through the Center for Precision-Assembled Quantum Materials (DMR-2011738), in collaboration with the National Research Foundation of Korea through the Global Research Laboratory Program (2016K1A1A2912707). Control experiments (Z.W.) were supported by the Department of Energy (DE-SC0016703). Synthesis of boron nitride (K.W. and T.T.) was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan (grant no. JPMXP0112101001), and JSPS KAKENHI (grant nos. JP19H05790 and JP20H00354).

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Authors and Affiliations

  1. Department of Mechanical Engineering, Columbia University, New York, NY, USA

    Yang Liu, Song Liu, Zhiying Wang, Baichang Li & James Hone

  2. Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan

    Kenji Watanabe

  3. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan

    Takashi Taniguchi

  4. SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Korea

    Won Jong Yoo

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Contributions

Y.L. conceived, led and was involved in all aspects of the project and performed all the design, fabrication, measurement, simulation and data analysis. S.L. grew the WSe2 crystals and performed the scanning tunnelling microscopy characterizations of the bulk WSe2 crystals. Z.W. performed the control experiments with evaporated contacts. K.W. and T.T. grew the hBN crystals. W.J.Y. and J.H. advised on the project. Y.L. and J.H. discussed the results and co-wrote the manuscript with input from all the authors.

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Correspondence to Yang Liu or James Hone.

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Nature Electronics thanks Takamasa Kawanago, Seongjun Park and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–15 and Sections 1–15.

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Liu, Y., Liu, S., Wang, Z. et al. Low-resistance metal contacts to encapsulated semiconductor monolayers with long transfer length. Nat Electron 5, 579–585 (2022). https://doi.org/10.1038/s41928-022-00808-9

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