100 GHz zinc oxide Schottky diodes processed from solution on a wafer scale

Abstract

Inexpensive radio-frequency devices that can meet the ultrahigh-frequency needs of fifth- and sixth-generation wireless telecommunication networks are required. However, combining high performance with cost-effective scalable manufacturing has proved challenging. Here, we report the fabrication of solution-processed zinc oxide Schottky diodes that can operate in microwave and millimetre-wave frequency bands. The fully coplanar diodes are prepared using wafer-scale adhesion lithography to pattern two asymmetric metal electrodes separated by a gap of around 15 nm, and are completed with the deposition of a zinc oxide or aluminium-doped ZnO layer from solution. The Schottky diodes exhibit a maximum intrinsic cutoff frequency in excess of 100 GHz, and when integrated with other passive components yield radio-frequency energy-harvesting circuits that are capable of delivering output voltages of 600 mV and 260 mV at 2.45 GHz and 10 GHz, respectively.

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Fig. 1: Fabrication of nanogap electrodes and radio-frequency Schottky diode structure.
Fig. 2: D.c. characteristics and operational principle of ZnO and Al–ZnO nanogap Schottky diodes.
Fig. 3: High-frequency operation of ZnO-based nanogap Schottky diodes.
Fig. 4: Output voltage capabilities of the ZnO-based rectifier.

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.

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Acknowledgements

D.G.G., J.S. and T.D.A. acknowledge financial support from the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement 706707, the European Research Council (ERC) project AMPRO under grant no. 280221, the Engineering and Physical Sciences Research Council (EPSRC) grant no. EP/P505550/1 and the EPSRC Centre for Innovative Manufacturing in Large Area Electronics (CIM-LAE) grant no. EP/K03099X/1. A.S., K.L., H.F. and T.D.A. acknowledge support by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award no. OSR-2018-CARF/CCF-3079. A.A.S. thanks SERB for an Early Research Career Award (ECR/2017/1562) and SRM IST for financial support. We also thank S. Kano for helpful discussion on the nanogap size analysis.

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T.D.A., D.G.G. and J.S. conceived the project. T.D.A. guided and supervised the project. D.G.G. and J.S. fabricated the small-scale devices and performed electrical measurements. D.G.G. analysed the data. A.A.S. set up the high-frequency rectifier circuit measurements and D.G.G., J.S. and A.A.S. analysed the data. D.G.G., H.F. and P.R. performed the single-port measurements and extracted and analysed the data. Y.-H.L. provided the Al-doped ZnO formulations. A.S., K.L. and H.F. carried out SEM and TEM characterization and performed statistical analysis on data derived from microscopy images. F.A. assisted with fabrication of wafer-scale devices and their electrical characterization. D.G.G. and T.D.A. wrote the first draft of the manuscript. All authors discussed the results and contributed to the final version of the paper.

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Correspondence to Dimitra G. Georgiadou or Thomas D. Anthopoulos.

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Supplementary Notes 1–7, Figs 1–14, Tables 1–3 and references.

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Georgiadou, D.G., Semple, J., Sagade, A.A. et al. 100 GHz zinc oxide Schottky diodes processed from solution on a wafer scale. Nat Electron 3, 718–725 (2020). https://doi.org/10.1038/s41928-020-00484-7

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