AVS 60th International Symposium and Exhibition
    Transparent Conductors and Printable Electronics Focus Topic Tuesday Sessions
       Session TC-TuP

Paper TC-TuP5
Influence of Rapid Thermal Annealing Treatment on Various Properties of Texture-Etched Al- or Ga-Doped ZnO Thin Films Deposited by Magnetron Sputtering

Tuesday, October 29, 2013, 6:00 pm, Room Hall B

Session: Transparent Conductors and Printable Electronics Poster Session
Presenter: T. Miyata, Kanazawa Institute of Technology, Japan
Authors: T. Minami, Kanazawa Institute of Technology, Japan
J. Nomoto, Kanazawa Institute of Technology, Japan
T. Miyata, Kanazawa Institute of Technology, Japan
T. Yamanaka, Kanazawa Institute of Technology, Japan
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This paper describes an investigation of the influence of a rapid thermal annealing (RTA) treatment on various properties of transparent conducting Al- or Ga-doped ZnO (AZO or GZO) thin films that was conducted in an effort to develop thin-film transparent electrodes suitable for thin-film solar cell applications. These doped ZnO thin films were deposited by an r.f. power superimposed d.c. magnetron sputtering deposition using AZO or GZO target : prepared with Al2O3 contents of 0.5-2 wt.% or Ga2O3 contents of 0.5-5.7 wt.%, respectively. The optical and electrical properties and texture-etched surface structures as well as the stability of electrical properties after use for long terms in moist environment in these thin films were found to be considerably influenced after heat treatment with RTA at 500oC for 5 min in air. In particular, the obtained electrical properties in these thin films were considerably dependent on the RTA treatment conditions as well as the kind and content of impurity doped into the films. For example, the heat treatment with RTA always decreased the carrier concentration in both the AZO and GZO films, irrespective of the doped impurity content, whereas the resulting carrier concentration in as-deposited AZO and GZO thin films increased as the impurity content doped into the films was increased. In addition, the Hall mobilities in both the AZO and GZO films doped with impurity contents up to approximately 1.25 at.% always decreased after heat treatment with RTA, which is in contrast to the slight increase of the Hall mobilities exhibited in films doped with an impurity content above approximately 1.5 at.%. The etch pit size developed in AZO and GZO films that were surface textured by wet-chemical etching in 0.2 mol./l HCl at 25oC tended to increase as the content of impurity doped in the films was increased up to approximately 2.5 at.%; however, the etch pit size obtained in GZO films decreased as this content was increased further. It should be noted that the heat treatment with RTA resulted in considerably enhanced etch pit size in these films, irrespective of the kind and content of doped impurity. As a result, in the films that were wet-chemically etched after being heat treated with RTA, the transmittance and the haze value in the near infrared range of 800-1200nm both increased as the size of the etch pits increased. It should be noted that the improvement in the transmittance and the haze value obtained in texture-etched AZO and GZO thin films heat treated with RTA is sufficient to enable the use of the surface textured these films described above for thin-film transparent electrode applications in thin-film solar cells.