A simple Al-doping method that is used to significantly enhance the operating characteristics of ZnO thin-film transistors processed from solution at temperatures down to 120 °C is reported. The two-step doping process relies on the dissolution of zinc oxide hydrate in ammonia hydroxide to form an aqueous Zn-ammine complex solution and the subsequent immersion of Al pellets into it at room temperature. The pellets are then removed, and the doped precursor solution is spin-coated onto the substrate followed by thermal annealing in air to form the n-doped ZnO:Al layers. By controlling the immersion time of the Al pellets in the precursor solution, the free electron concentration in ZnO can be tuned. The resulting ZnO:Al layers are shown to be polycrystalline with tuneable electrical properties. ZnO:Al-based transistors processed at 180 °C exhibit enhanced electron mobility when compared to intrinsic ZnO devices with the maximum values exceeding 5 cm2 V−1 s−1. Even when the process temperature is reduced to 120 °C, the ZnO:Al transistors retain their excellent operating characteristics with a maximum electron mobility of 3 cm2 V−1 s−1. This is amongst the highest values reported to date for soluton-deposited ZnO transistors processed at 120 °C in air.
Bibliographical noteFunding Information:
Y.-H.L., S.R.T., H.F., and T.D.A. are grateful to Dutch Polymer Institute (DPI) S-PLORE grant no. 735 and European Research Council (ERC) AMPRO Project No. 280221 for financial support.
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- aluminum doping
- solution processing
- thin-film transistors
- transparent electronics
- zinc oxide
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials