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Nanometre-thin indium tin oxide for advanced high-performance electronics

Abstract

Although indium tin oxide (ITO) is widely used in optoelectronics due to its high optical transmittance and electrical conductivity, its degenerate doping limits exploitation as a semiconduction material. In this work, we created short-channel active transistors based on an ultra-thin (down to 4 nm) ITO channel and a high-quality, lanthanum-doped hafnium oxide dielectric of equivalent oxide thickness of 0.8 nm, with performance comparative to that of existing metal oxides and emerging two-dimensional materials. Short-channel immunity, with a subthreshold slope of 66 mV per decade, off-state current <100 fA μm–1 and on/off ratio up to 5.5 × 109, was measured for a 40-nm transistor. Logic inverters working in the subthreshold regime exhibit a high gain of 178 at a low-supply voltage of 0.5 V. Moreover, radiofrequency transistors, with as-measured cut-off frequency fT and maximum oscillation frequency fmax both >10 GHz, have been demonstrated. The unique wide bandgap and low dielectric constant of ITO provide prospects for future scaling below the 5-nm regime for advanced low-power electronics.

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Fig. 1: Material characterization of thin ITO film.
Fig. 2: Device structure and direct current electrical characteristics.
Fig. 3: Off-state and on-state performance of ITO transistors.
Fig. 4: Logic inverters based on ITO transistors with high gain.
Fig. 5: High performance of RF transistors based on ITO.

Data availability

The data supporting the figures within this paper are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (grant nos. 61574066 and 61874162), the 111 Project (no. B18001) and the Strategic Priority Research Programme of Chinese Academy of Sciences (grant no. XDB30000000). The authors thank the staff at the Center of Micro-fabrication and Characterization of Wuhan National Laboratory for Optoelectronics, and Huazhong University of Science and Technology Analytical and Testing Center, for support with the RF magnetron sputtering system, electron-beam lithography, electron-beam evaporation and transmission electron microscopy and ultraviolet-visible spectrophotometer measurements; and M. Huang for useful discussions.

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Contributions

Y.W. proposed and supervised the project. S.L. and M.W. fabricated the devices. S.L. performed morphology and electrical measurements. S.L., M.T., Q.G. and T.L. performed the RF characterizations. S.L. and Q.H. discussed the device designs. S.L., X.L. and Y.W. analysed the data. S.L. and Y.W. co-wrote the paper. All authors contributed to discussions on the manuscript.

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Correspondence to Yanqing Wu.

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Supplementary Sections 1–5, Supplementary Figs. 1–40, Supplementary Tables 1–7 and supplementary refs. 1–74.

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Li, S., Tian, M., Gao, Q. et al. Nanometre-thin indium tin oxide for advanced high-performance electronics. Nat. Mater. 18, 1091–1097 (2019). https://doi.org/10.1038/s41563-019-0455-8

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