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Radiofrequency transistors based on aligned carbon nanotube arrays

Abstract

The development of next-generation wireless communication technology requires integrated radiofrequency devices capable of operating at frequencies greater than 90 GHz. Carbon nanotube field-effect transistors are promising for such applications, but key performance metrics, including operating frequency, at present fall below theoretical predictions. Here we report radiofrequency transistors based on high-purity carbon nanotube arrays that are fabricated using a double-dispersion sorting and binary liquid interface aligning process. The nanotube arrays exhibit a density of approximately 120 nanotubes per micrometre, a maximum carrier mobility of 1,580 cm2 V−1 s−1 and a saturation velocity of up to 3.0 × 107 cm s−1. The resulting field-effect transistors offer high d.c. performance (on-state current of 1.92 mA µm−1 and peak transconductance of 1.40 mS μm−1 at a bias of −0.9 V) for operation at millimetre-wave and terahertz frequencies. Transistors with a 50 nm gate length show current-gain and power-gain cutoff frequencies of up to 540 and 306 GHz, respectively, and radiofrequency amplifiers can exhibit a high power gain (23.2 dB) and inherent linearity (31.2 dBm output power of the third-order intercept point) in the K-band (18 GHz).

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Fig. 1: Preparation and characterization of aligned CNT arrays.
Fig. 2: Structure and characteristics of CNT-array-based FETs on quartz substrates.
Fig. 3: Electric characteristics of CNT-array-based transistors on high-resistivity Si/SiO2 substrates.
Fig. 4: RF performance characteristics of CNT-array-based high-speed transistors on high-resistivity Si/SiO2 substrates.
Fig. 5: Power gain and linearity characteristics of a CNT-array-based RF amplifier on a silicon wafer.

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

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Acknowledgements

We thank C. Jin (Zhejiang University) and S. Ding (Xiangtan University) for TEM technique support, and H. Liu and B. Sun (Institute of Microelectronics of the Chinese Academy of Sciences) for S-parameter, single-tone and two-tone measurement support. This work is supported by the National Key Research & Development Program (grant no. 2016YFA0201901), the National Science Foundation of China (grant nos. 61888102 and 61671020) and the Beijing Municipal Science and Technology Commission (grant no. Z181100004418011).

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Contributions

Z.Z. and L.-M.P. proposed and supervised the project. H.S. and D.Z. performed device fabrication and d.c. measurements. D.Z. and H.S. designed and optimized the three-dimensional geometry of G/S/D electrodes and gate dielectric thickness. D.Z. and H.S. designed the multi-finger RF device structure. J.H. and H.W. produced the aligned CNT arrays. H.S., L.L., D.Z. and J.H. characterized the CNT materials. H.S. and L.L. performed the polarized Raman spectroscopy characterization. L.X. performed the mobility and saturation velocity simulations using a virtual source model. D.Z. and H.S. performed the small-signal model simulations. H.S., D.Z., P.S. and L.F. performed the S-parameter measurements. H.S., D.Z., L.D. and J.Z. performed the single-tone and two-tone tests. H.S., L.D., D.Z., Z.Z. and L.-M.P. analysed the data. H.S., L.D., Z.Z. and L.-M.P. co-wrote the manuscript. All the authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Zhiyong Zhang or Lian-Mao Peng.

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Peer review information Nature Electronics thanks Qingwen Li and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Shi, H., Ding, L., Zhong, D. et al. Radiofrequency transistors based on aligned carbon nanotube arrays. Nat Electron 4, 405–415 (2021). https://doi.org/10.1038/s41928-021-00594-w

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