High tunnelling electroresistance in a ferroelectric van der Waals heterojunction via giant barrier height modulation

Abstract

Ferroelectric tunnel junctions use a thin ferroelectric layer as a tunnelling barrier, the height of which can be modified by switching its ferroelectric polarization. The junctions can offer low power consumption, non-volatile switching and non-destructive readout, and thus are promising for the development of memory and computing applications. However, achieving a high tunnelling electroresistance (TER) in these devices remains challenging. Typical junctions, such as those based on barium titanate or hafnium dioxide, are limited by their small barrier height modulation of around 0.1 eV. Here, we report a ferroelectric tunnel junction that uses layered copper indium thiophosphate (CuInP2S6) as the ferroelectric barrier, and graphene and chromium as asymmetric contacts. The ferroelectric field effect in CuInP2S6 can induce a barrier height modulation of 1 eV in the junction, which results in a TER of above 107. This modulation, which is shown using Kelvin probe force microscopy and Raman spectroscopy, is due to the low density of states and small quantum capacitance near the Dirac point of the semi-metallic graphene.

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Fig. 1: The vdW FTJ device structure and the ferroelectric property of CIPS.
Fig. 2: Electrical characteristics of the vdW FTJ.
Fig. 3: Origin of the giant TER.
Fig. 4: Effect of the graphene semi-metallic contact on the vdW FTJ characteristics.
Fig. 5: Performance of the vdW FTJ as a memory device.

Data availability

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

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Acknowledgements

J.W., H.-Y.C. and H.W. acknowledge support from the Army Research Office Young Investigator Program (grant W911NF-18-1-0268) and the National Science Foundation (grant CCF-1618038). N.Y. and J.G. acknowledge support from the National Science Foundation (grants 1618762, 1610387 and 1904580). J.C. and X.L. acknowledge support from the Semiconductor Research Corporation (SRC).

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Contributions

H.W. conceived the project and led the overall research activities. J.W. and H.-Y.C. fabricated the vdW FTJ devices. J.W., H.-Y.C. and X.Y. performed the electrical measurements and data analysis. N.Y. and J.G. led the research in the theoretical modelling. J.C. and X.L. synthesized the materials. J.W. and F.L. characterized the materials and devices. Q.S. contributed to the formulation of the project idea. J.W., H.-Y.C. and H.W. co-wrote the manuscript with input and comments from all the authors.

Corresponding authors

Correspondence to Qibin Sun or Jing Guo or Han Wang.

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Supplementary Figs. 1–10, Notes 1–3 and refs. 1 and 2.

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Wu, J., Chen, H., Yang, N. et al. High tunnelling electroresistance in a ferroelectric van der Waals heterojunction via giant barrier height modulation. Nat Electron 3, 466–472 (2020). https://doi.org/10.1038/s41928-020-0441-9

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