4 March 2013 Nanolithography for 3-dimentional nanostructures: enhancement of light output power in vertical light emitting diodes
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Abstract
We review the recent developments to enhance the external quantum efficiency (EQE) in GaN based vertical light-emitting diodes (V-LEDs). The controlling of side-wall angle by SiO2 nanosphere lithography significantly improved the light extraction efficiency (LEE) of V-LEDs; this result is 6% higher than the photo chemical etching (PCE) method, which is known to have the highest light extraction, and 300% higher than flat surface V-LEDs. Nanostructured V-LEDs with a very dense forest of vertically aligned ZnO nanowires on the surface of N-face n-GaN induce the dramtic improvement in LEE. The structural transformation at the nanolevel by the UV radiation and Ozone (UV-O) treatment contributes the high density of Zn seed on GaN, and then this approach shows an extreme enhancement in LEE (>2.8x) compared to flat V-LEDs. The enhanced LEE was also demonstrated by depositing a spontaneously formed MgO nano-pyramids and ZnO refractive-index modulation layer on the surface of V-LEDs, resulting in the increase of output power by 49 %, comparing with the V-LEDs with a flat n-GaN surface. The enhancement of light output power by the nanotexturing of n-face n-GaN was remarkably influenced by 3-dimentional nanostructures.
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Yang Hee Song, Jun Ho Son, Buem Joon Kim, Jong-Lam Lee, "Nanolithography for 3-dimentional nanostructures: enhancement of light output power in vertical light emitting diodes", Proc. SPIE 8625, Gallium Nitride Materials and Devices VIII, 86250R (4 March 2013); doi: 10.1117/12.2004038; https://doi.org/10.1117/12.2004038
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