High-efficiency AlGaN deep-UV LEDs fabricated on a- and m-axis oriented c-plane sapphire substrates

Authors

  • Sachie Fujikawa,

    Corresponding author
    1. RIKEN (The Institute of Physics and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
    2. JST- CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
    • Phone: +81-48-462-1254, Fax: +81-48-467-1960
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  • Hideki Hirayama,

    1. RIKEN (The Institute of Physics and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
    2. JST- CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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    • Phone: +81-48-462-1254, Fax: +81-48-462-1276

  • Noritoshi Maeda

    1. RIKEN (The Institute of Physics and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
    2. JST- CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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Abstract

We demonstrated high-efficiency 270 nm-band AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) fabricated on 0.15° off a- and m-axis oriented c-plane (0001) sapphire substrates grown by low-pressure metal organic chemical-vapor deposition (LP-MOCVD). An approximately 4.5 μm-thick low threading dislocation density (TDD) AlN template was grown on the sapphire substrate by using an NH3 pulsed-flow multilayer (ML) growth method. We found that atomically flat surface can be easily obtained for AlN layer grown on a-axis oriented sample. On the other hand, a step-bunching was observed for the surface of AlN layer grown on m-axis oriented sample. We found, from these results, that a-axis oriented (0001) sapphire is more suitable for obtaining a flat surface in AlN template without step-bunching. We also found that shorter wavelength LED can be obtained by using an a-axis oriented (0001) sapphire, because an Al incorporation in AlGaN is slightly high for the growth on a-axis oriented (0001) sapphire. We achieved high-efficiency AlGaN quantum well (QW) DUV LEDs on AlN templates grown on both a- and m-axis oriented sapphire substrates. The peak wavelengths of the LEDs fabricated on a- and m-axis oriented sapphire were 270 and 277 nm, respectively. The maximum external quantum efficiencies (EQEs) of the LEDs fabricated on a- and m-axis oriented sapphire were 3.8 and 3.2%, respectively, measured under room temperature (RT) continuous wave (CW) operations. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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