Open AccessOptimal length of ZnO nanorods for improving the light-extraction efficiency of blue InGaN light-emitting diodes
Author(s) -
Hyun Jeong,
Rafael SalasMontiel,
Mun Seok Jeong
Publication year - 2015
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.023195
Subject(s) - light emitting diode , materials science , optoelectronics , nanorod , diode , photoluminescence , raman spectroscopy , optics , finite difference time domain method , wide bandgap semiconductor , nanotechnology , physics
Optimal length of ZnO nanorods (NRs) on blue InGaN light-emitting diodes (LEDs) was investigated to improve the light-extraction efficiency (LEE) of the LED. X-ray diffraction, photoluminescence spectroscopy, and micro-Raman spectroscopy were employed to determine the structural and optical properties of the ZnO NRs with length of 300 nm and 5 μm grown by a hydrothermal method. From the conventional light output power versus injection current (L-I) measurement, we found that the light output power of the LEDs with 300-nm- and 5-μm-long ZnO NRs was approximately 14.6% and 40.7% greater, respectively, than that of the LED without the ZnO NRs at an operating current of 20 mA. In addition, there were almost no changes to the electrical properties of the ZnO-NR-coated LEDs. The effect of the length of the ZnO NRs on the LEE of the LEDs was theoretically verified with three-dimensional finite-difference time-domain (FDTD) analysis. The FDTD images of the optical power and far-field radiation patterns of the LEDs showed that more photons were guided to the out of the LED by the longer ZnO NRs than by the shorter ZnO NRs grown on the LEDs.