AVS 57th International Symposium & Exhibition
    Energy Frontiers Topical Conference Thursday Sessions
       Session EN-ThP

Paper EN-ThP2
Optical and Electrical Properties of Transparent Conducting B-doped ZnO Thin Films Prepared by Various Deposition Methods

Thursday, October 21, 2010, 6:00 pm, Room Southwest Exhibit Hall

Session: Energy Frontiers Topical Conference Poster Session
Presenter: T. Miyata, Kanazawa Institute of Technology, Japan
Authors: J.-I. Nomoto, Kanazawa Institute of Technology, Japan
S. Hotta, Kanazawa Institute of Technology, Japan
T. Miyata, Kanazawa Institute of Technology, Japan
T. Minami, Kanazawa Institute of Technology, Japan
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Recently, transparent conducting impurity-doped ZnO films with a high transmittance in the near-infrared region have attracted much attention for transparent electrode applications in thin-film solar cells. It is necessary to achieve a reduction of the plasma resonance frequency resulting from a decrease of carrier concentration. However, in order to maintain a low resistivity in impurity-doped ZnO films, any decrease in carrier concentration should be compensated by an appropriate increase of mobility. In this paper, we describe the preparation of transparent conducting B-doped ZnO (BZO) thin films with a lower carrier concentration as well as a higher Hall mobility by various deposition methods. BZO thin films were prepared on low temperature glass substrates by dc or rf magnetron sputtering deposition, pulsed laser deposition (PLD) and vacuum arc plasma evaporation methods. The optical and electrical properties were evaluated in BZO thin films prepared with various thicknesses up to about 3 μm and doped B contents (B/(B+Zn) atomic ratio) up to 5 at.%. In addition, long-term resistivity stability was evaluated with exposure to a highly moist environment (air at 85% relative humidity and 85oC) as well as an oxidizing atmosphere at a high temperature (air at a temperature up to 250oC). In the moisture-resistance tests, the BZO thin films exhibited an increase in resistivity during long-term testing; increasing the thin film thickness tended to lessen this increase in resistance, irrespective of the deposition method. In the heat-resistance tests, the resistivity of thin films thicker than approximately 200 nm was found to be stable for 1000 h at a testing temperature up to 200oC. A Hall mobility of 42 cm2/Vs and a carrier concentration of 3.4×1020 cm-3 were obtained in a BZO thin film prepared by PLD. Resistivities of 4-6×10-4 Ωcm were obtained in 500 nm-thick-BZO thin films prepared with a B content of 1 at.%, irrespective of deposition methods. The low-resistivity BZO thin films exhibited an average transmittance in the visible range above 80 %; transmittances were above 80% at a wavelength of 1100 nm and 75% at 1300 nm.