Optimization of Light Extraction Efficiency of III-Nitride LEDs With Self-Assembled Colloidal-Based Microlenses

Author

Ee, Yik-Khoon ; Kumnorkaew, Pisist ; Arif, Ronald A. ; Tong, Hua ; Zhao, Hongping ; Gilchrist, J.F. ; Tansu, Nelson

Author_Institution

Dept. of Electr. & Comput. Eng., Lehigh Univ., Bethlehem, PA, USA

Volume

15

Issue

4

fYear

2009

Firstpage

1218

Lastpage

1225

Abstract

Improvement of light extraction efficiency of InGaN LEDs using colloidal-based SiO₂/polystyrene (PS) microlens arrays was demonstrated. The size effect of the SiO₂ microspheres and the thickness effect of the PS layer on the light extraction efficiency of III-nitride LEDs were studied. The monolayer rapid convective deposition conditions for SiO₂ microspheres were also investigated. Ray tracing simulations show that the use of microlens arrays can lead to increase in light extraction efficiency of InGaN LEDs by 2.64 times. This is consistent with experiments that demonstrated 2.49 times improvement in light extraction utilizing SiO₂/PS microlens arrays. The enhancement in light extraction efficiency is attributed to increase in effective photon escape cone due to SiO₂/PS microlens arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN/SiO₂/PS/air interface.

Keywords

III-V semiconductors; gallium compounds; indium compounds; integrated optics; light emitting diodes; microlenses; optical arrays; polymers; ray tracing; refractive index; self-assembly; silicon compounds; wide band gap semiconductors; Fresnel reflection; III-nitride LEDs; InGaN; colloids; effective photon escape; light extraction efficiency; microlens arrays; microspheres; monolayer rapid convective deposition; polystyrene; ray tracing simulations; refractive index; self-assembly; Colloid; InGaN quantum wells (QWs); LEDs; light extraction efficiency; microlens arrays;

fLanguage

English

Journal_Title

Selected Topics in Quantum Electronics, IEEE Journal of

Publisher

ieee

ISSN

1077-260X

Type

jour

DOI

10.1109/JSTQE.2009.2015580

Filename

5061625