Enhancement of light extraction in GaN-based light-emitting diodes by Al2O3-coated ZnO nanorod arrays

We report on the improvement of light extraction efficiency in blue light-emitting diodes (LEDs) by the use of Al2O3/ZnO core/shell nanorods (NRs) grown on the surface of the LED epi-structure. The electroluminescence intensity at a current injection of 20 mA of LEDs with 40 nm-thick Al2O3-coated ZnO NR arrays is 2.1 and 4.0 times than those of LEDs with bare ZnO NRs and no NRs, respectively. The enhanced light extraction of LEDs with Al2O3-coated ZnO NRs can be attributed to an increase in transmission and improved light extraction probability for photons generated in blue LEDs due to a reduction of Fresnel reflection loss. (C) 2014 Elsevier B.V. All rights reserved.This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (NRF- 2012R1A1A1041930 )