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Improvement of photon extraction efficiency of GaN-based LED using micro and nano complex polymer structures

Joong-Yeon Cho1, Kyeong-Jae Byeon1, Hyoungwon Park1, Jinseung Kim1, Hyeong-Seok Kim2 and Heon Lee1*

Author Affiliations

1 Department of Materials Science and Engineering, Korea University, Anam-dong 5-ga, Seongbuk-gu, Seoul 136-713, South Korea

2 Department of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756, South Korea

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Nanoscale Research Letters 2011, 6:578  doi:10.1186/1556-276X-6-578

Published: 31 October 2011

Abstract

A micro- and nanoscale complex structure made of a high refractive index polymer (n = 2.08) was formed on the ITO electrode layer of an edge-emitting type GaN blue light-emitting diode (LED), in order to improve the photon extraction efficiency by suppressing total internal reflection of photons. The nanoimprint lithography process was used to form the micro- and nanoscale complex structures, using a polymer resin with dispersed TiO2 nano-particles as an imprint resin. Plasma processing, such as reactive ion etching, was used to form the micro- and nano-scale complex structure; thus, plasma-induced damage to the LED device can be avoided. Due to the high refractive index polymeric micro- and nanostructure on the ITO layer, the electroluminescence emission was increased up to 20%, compared to an identical LED that was grown on a patterned sapphire substrate to improve photon extraction efficiency.