| AVS 65th International Symposium & Exhibition | |
| Advanced Surface Engineering Division | Tuesday Sessions |
| Session SE-TuP |
| Session: | Advanced Surface Engineering Division Poster Session |
| Presenter: | J.H. Lee, Chang Gung University, Taiwan |
| Authors: | J. Lee, Chang Gung University, Taiwan Y. Lin, Chang Gung University, Taiwan G. Wu, Chang Gung University, Taiwan |
| Correspondent: | Click to Email |
It has been known that high refractive index material such as gallium nitride film has been limited for light extraction by low total internal reflection angle. The external quantum efficiency for a light-emitting diode is thus low due to absorption by the semiconductor material and the substrate. In this paper, we proposed to use homeotropic, vertical alignment, liquid crystal polymer coatings on patterned SiO2 micro - pillar arrays to improve the light extraction of nitride light-emitting diodes . A wet etching technique was firstly employed to create the patterned SiO2 micro-pillar arrays on the surface. The pillar was nominally 3 μm in diameter, 200-600 nm in height, and the period was 6 μm for a triangular array. Then we coated 5 wt% liquid crystal polymer precursor uniformly on the surface of the etched structure. The results showed that the homeotropic optical thin-film improved light guiding, and the light escape cone angle increased from 26 to 50-60 degrees by the viewing angle test system at an injection current of 20 mA. The light extraction efficiency was also increased by 59% by using an integrating sphere.
Keywords: Liquid crystal polymer, Light-emitting diode, SiO2 micro - pillar
This work was supported in part by the Ministry of Science and Technology under research grants MOST105-2221-E182-059-MY3 and CMRPD2E0481.