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Spin-on glass structures are built directly on an indium tin oxide surface by imprinting lithography to improve the optical efficiency of GaN-based blue LEDs. Two different mold materials, sapphire and silicon, are fabricated via conventional UV lithography and a wet etching process. In the UV lithography, the 750-nm linewidth mask directly contacts the thin photoresist to make a good resolution pattern. Our study shows that the periodic surface structures made via imprinting enhance the light-extraction efficiency-surface texturing reduces the total internal reflection and Fresnel reflection when light is generated by active layers of the LEDs. The light output power values of the conventional LED and imprinting nanohole-array LEDs are 21.7 and 27.3 mW, respectively, under 150-mA current injections.
Date of Publication: May 2011