AVS 56th International Symposium & Exhibition
    Thin Film Thursday Sessions
       Session TF-ThP

Paper TF-ThP15
Resistivity Characteristics of Transparent Conducting Impurity-doped ZnO Films for Use in Oxidizing Environments at High Temperatures

Thursday, November 12, 2009, 6:00 pm, Room Hall 3

Session: Aspects of Thin Films Poster Session
Presenter: J. Nomoto, Kanazawa Institute of Technology, Japan
Authors: J. Nomoto, Kanazawa Institute of Technology, Japan
M. Konagai, Kanazawa Institute of Technology, Japan
T. Miyata, Kanazawa Institute of Technology, Japan
T. Minami, Kanazawa Institute of Technology, Japan
Correspondent: Click to Email
For the purpose of determining the most suitable material to use as transparent electrodes in thin-film solar cells, this paper compares in detail the resistivity behavior of transparent conducting Al-doped ZnO (AZO ) and Ga-doped ZnO (GZO) thin films for use in oxidizing environments at high temperatures. These thin films with thicknesses in the range from approximately 100 to 3000 nm were prepared on glass substrates at a temperature of 200oC by either an rf superimposed dc or a conventional dc magnetron sputtering deposition (rf+dc-MSD or dc-MSD). The obtained resistivities in AZO and GZO thin films prepared by rf+dc-MSD were always lower than those in films prepared by dc-MSD. However, the obtainable resistivity of the thin films prepared by an rf+dc-MSD using lower resistivity targets was not decreased more sufficient than that of thin films prepared by a conventional dc-MSD with the same targets, whereas the obtained resistivity decreased as the resistivity of targets used was decreased. In moisture-resistant tests, resistivity change was measured over time with exposure to a highly moist environment (air at 85% relative humidity and 85oC). The resistivity stability of GZO thin films over long term testing was found to be always lower than that of AZO thin films prepared with the same thickness under the same deposition conditions. In heat-resistance tests, resistivity was measured both before and after heat treatment in an oxidizing atmosphere (30 min. in air at a temperature up to 400oC). The resistivity stability of AZO thin films during heat testing at 400oC was found to be always lower than that of GZO thin films prepared with the same thickness under the same deposition conditions. It was also found that the increase of resistivity observed in AZO films was related to decreases of both the carrier concentration and the Hall mobility, but, in contrast, that observed in GZO films was mainly attributable to a decrease of carrier concentration. The difference of resistivity behavior in the heat tests was mainly attributed to the micro-structural difference associated with the crystallinity of deposited films.