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Integration of high-κ native oxides of gallium for two-dimensional transistors

Nature Electronics volume 7, pages 1126–1136 (2024)Cite this article

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Abstract

The deposition of a metal oxide layer with good dielectric properties is a critical step in fabricating the gate dielectric of transistors based on two-dimensional semiconductors. However, current techniques for depositing ultrathin metal oxide layers on two-dimensional semiconductors suffer from quality issues that can compromise transistor performance. Here, we show that an ultrathin and uniform native oxide of gallium (Ga2O3) that naturally forms on the surface of liquid metals in an ambient environment can be prepared on the surface of molybdenum disulfide (MoS2) by squeeze-printing and surface-tension-driven methods. The Ga2O3 layer possesses a high dielectric constant of around 30 and equivalent oxide thickness of around 0.4 nm. Due to the good dielectric properties and van der Waals integration, MoS2 transistors with Ga2O3 gate dielectrics exhibit a subthreshold swing down to 60 mV dec−1, an on/off ratio of 108 and a gate leakage down to around 4 × 10−7 A cm−2.

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Fig. 1: Integration of Ga2O3 as a dielectric layer.
Fig. 2: Device configuration of a top-gated MoS2 FET with a Ga2O3 dielectric layer.
Fig. 3: Dielectric properties of Ga2O3.
Fig. 4: MoS2 FET performance with Ga2O3 dielectric layer.
Fig. 5: Logic gates with a Ga2O3 dielectric layer.

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Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

Z.L. acknowledges support from the National Research Foundation, Singapore, under its Competitive Research Programme (Grant No. NRF-CRP22-2019-0007) and its NRF-ISF joint research program (Grant No. NRF2020-NRF-ISF004-3520). This research is also supported by A*STAR under an AME IRG grant (Project No. A2083c0052) and A*STAR MTC Programmatic Grant (Grant No. M23M2b0056). The microwave microscopy work (S.F. and K.L.) is supported by the Welch Foundation (Grant No. F-1814). The nanoindentation work (Q.F. and J.L) is supported by the Welch Foundation (Grant No. C-1716).

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Author notes

  1. These authors contributed equally: Kongyang Yi, Wen Qin.

Authors and Affiliations

  1. School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore

    Kongyang Yi, Yao Wu, Xun Cao, Ya Deng, Chao Zhu & Zheng Liu

  2. State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, China

    Wen Qin, Zhili Hu & Zhuhua Zhang

  3. State Key Laboratory of Materials for Integrated Circuits, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China

    Yamin Huang & Yemin Dong

  4. Department of Physics, University of Texas at Austin, Austin, TX, USA

    Shaopeng Feng & Keji Lai

  5. Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA

    Qiyi Fang & Jun Lou

  6. School of Electronic Science and Engineering, Nanjing University, Nanjing, China

    Xilu Zou & Xinran Wang

  7. Suzhou Laboratory, Suzhou, China

    Xilu Zou, Taotao Li & Xinran Wang

  8. Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore

    Kah-Wee Ang

  9. School of Integrated Circuits, Nanjing University, Suzhou, China

    Taotao Li & Xinran Wang

  10. Interdisciplinary Research Center for Future Intelligent Chips (Chip-X), Nanjing University, Suzhou, China

    Taotao Li & Xinran Wang

  11. School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, New South Wales, Australia

    Kourosh Kalantar-Zadeh

  12. CINTRA CNRS/NTU/THALES, Singapore, Singapore

    Zheng Liu

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Contributions

Z.L. and K.Y. conceived and designed the project. K.Y. performed the OM, AFM, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, device fabrication, electrical measurements and data analysis. Y.H., Y.W., X.C. and Y. Dong contributed to the preparation of focused-ion-beam samples and cross-sectional STEM characterizations. W.Q., Z.H. and Z.Z. performed the DFT calculations. Y.W. performed the STEM, EDS and electron energy loss spectroscopy characterizations. S.F. and K.L. performed the tuning-fork-based microwave impedance microscopy measurements. Q.F. and J.L. performed the indentation measurements. X.Z., T.L. and X.W. provided the wafer-scale MoS2. K.-W.A. helped with the low-temperature measurements. Y. Deng prepared the CVD MoS2 single crystals and performed the Raman measurements. C.Z. commented on the manuscript and helped analyse the data. K.K.-Z. helped revise the manuscript. K.Y. and Z.L. summarized the manuscript. All authors contributed to discussions.

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Correspondence to Kongyang Yi or Zheng Liu.

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Nature Electronics thanks Mohammad Bagher Ghasemian, Yuxuan Cosmi Lin and He Tian for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Table 1 and Figs. 1–40.

Supplementary Video 1

Surface-tension-driven preparation.

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Yi, K., Qin, W., Huang, Y. et al. Integration of high-κ native oxides of gallium for two-dimensional transistors. Nat Electron 7, 1126–1136 (2024). https://doi.org/10.1038/s41928-024-01286-x

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