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


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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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.

Author information




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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