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Enhancing Light Emission of Nanostructured Vertical Light-Emitting Diodes by Minimizing Total Internal Reflection

Authors

  • Byeong-Uk Ye,

    1. School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
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  • Buem Joon Kim,

    1. Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
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  • Yang Hee Song,

    1. Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
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  • Jun Ho Son,

    1. Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
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  • Hak ki Yu,

    1. Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
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  • Myung Hwa Kim,

    1. Department of Chemistry & Nano Science, Ewha Womans University, Seoul, 120-750, Republic of Korea
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  • Jong-Lam Lee,

    Corresponding author
    1. Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
    • Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea
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  • Jeong Min Baik

    Corresponding author
    1. School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea
    • School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.
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Abstract

Nanostructured vertical light-emitting diodes (V-LEDs) with a very dense forest of vertically aligned ZnO nanowires on the surface of N-face n-type GaN are reported with a dramatic improvement in light extraction efficiency (∼3.0×). The structural transformation (i.e., dissociation of the surface nitrogen atoms) at the nanolevel by the UV radiation and Ozone treatments contributes significantly to the initial nucleation for the nanowires growth due to the interdiffusion of Zn into GaN, evident by the scanning photoemission microscopy (SPEM), high-resolution transmission electron microscopy (HR-TEM), and ultraviolet photoelectron spectroscopy (UPS) measurements. This enables the growth of densely aligned ZnO nanowires on N-face n-type GaN. This approach shows an extreme enhancement in light extraction efficiency (>2.8×) compared to flat V-LEDs, in good agreement with the simulation expectations (∼3.01×) obtained from 3D finite-difference time-domain (FDTD) tools, explained by the wave-guiding effect. The further increase (∼30%) in light extraction efficiency is also observed by optimized design of nanogeometry (i.e., MgO layer on ZnO nanorods).

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