Front Cover: Fabrication of transparent conducting polymer/GaN Schottky junction for deep level defect evaluation under light irradiation (Phys. Status Solidi A 3/20123)

Authors

  • Mickaël Lozac'h,

    1. Photonic Material Unit, National Institute for Materials Science, Tsukuba 305-0044, Japan
    2. Doctoral Program in Materials Science and Engineering, Tsukuba University, Tsukuba 305-8573, Japan
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  • Yoshitaka Nakano,

    1. Institute of Science and Technology Research, Chubu University, Kasugai, Aichi 487-8501, Japan
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  • Liwen Sang,

    1. ICYS-MANA, National Institute for Materials Science, Tsukuba 305-0044, Japan
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  • Kazuaki Sakoda,

    1. Photonic Material Unit, National Institute for Materials Science, Tsukuba 305-0044, Japan
    2. Doctoral Program in Materials Science and Engineering, Tsukuba University, Tsukuba 305-8573, Japan
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  • Masatomo Sumiya

    Corresponding author
    1. Wide Bandgap Materials Group, National Institute for Materials Science, Tsukuba 305-0044, Japan
    2. JST-ALCA, Japan Science and Technology Agency, Tokyo 102-0076, Japan
    • Phone: +81 29 860 4784, Fax: +81 29 851 4005
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Abstract

original image

The analysis of deep level defects of III-V nitrides (such as GaN or InxGa1-xN) is critical for the improvement of solar cell properties using these materials as an active layer. Schottky junctions are often used for the detection of level defects by deep level transient spectroscopy or deep level optical spectroscopy. Masatomo Sumiya and coworkers (pp. 470–473) have fabricated a transparent conducting polymer / GaN Schottky junction by using spin coating technique. The Schottky properties exhibited an ideal factor of 1.3, a Schttoky barrier height of 1.15 eV and a leakage current at -10 V of ∼10-6 mA/cm2, which was much better than that of a normal Schottky junction using a high workfunction metal like Au. Under irradiation of an AM1.5G solar simulator, the device performed an open circuit voltage of 0.72 V with a high fill factor of 0.71. Utilizing the features of transparency and good Schottky properties, the depletion layer in GaN at the interface beneath the conducting polymer was evaluated under light irradiation in order to detect the defects located in the GaN band-gap which must give an influence on the photovoltaic properties. This technique can be applied also to InGaN films with lower band-gap, even more suitable as photovoltaic material of III-V nitride film.

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