Design of p-CuO/n-ZnO heterojunctions by rf magnetron sputtering

Authors

  • Kachirayil J. Saji,

    1. Laboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
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  • Sascha Populoh,

    1. Laboratory for Solid State Chemistry and Catalysis, Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
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  • Ayodhya N. Tiwari,

    1. Laboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
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  • Yaroslav E. Romanyuk

    Corresponding author
    • Laboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
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Corresponding author: e-mail yaroslav.romanyuk@empa.ch, Phone: +41 58 765 4169, Fax: +41 58 765 1122

Abstract

Thin film heterojunctions of p-CuO/n-ZnO are prepared by magnetron sputtering and their electrical properties are investigated without and with external illumination. Radio-frequency (rf) sputtering in reactive oxygen–argon atmosphere is optimized to achieve phase-pure p-CuO thin films with mobilities up to 6.6 cm2 Vs−1 and hole concentrations in the order of 1017 cm−3. Intrinsic ZnO and conducting ZnO:Al are deposited by rf magnetron sputtering to form heterojunctions with CuO in both substrate and superstrate configurations with various Ohmic contacts to p-CuO. Heterojunctions in the substrate configuration do not possess diode properties, while devices in the superstrate configuration show clear rectifying characteristics with a threshold voltage (VTH) of 0.66 V and a forward-to-reverse current ratio of ∼450 at VTH. These junctions exhibit a weak photovoltaic effect under illumination, but reasons for the poor photoresponse are still to be identified.

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