[OPTICAL REVIEW Vol. 17, No. 4 (2010) 379-384]
© 2010 The Japan Society of Applied Physics
Functional Imprinting Structures on GaN-Based Light-Emitting Diodes for Light Pattern Modulation and Light Extraction Efficiency Enhancement
Sheng-Han TU*, Shang-Yen WU, Yeeu-Chang LEE1, Jui-Wen PAN2, Cheng-Huang KUO, Chih-Ming WANG3, and Jenq-Yang CHANG
Department of Optics and Photonics, National Central University, Jhongli, Taiwan 32001, R.O.C.
1Department of Mechanical Engineering, Chung Yuan Christian University, Jhongli, Taiwan 32023, R.O.C.
2Institute of Photonic System, College of Photonics National Chiao Tung University at Tainan, Tainan County, Taiwan 71150, R.O.C.
3Institute of Opto-Electronic Engineering, National Dong Hwa University, Hualien, Taiwan 97401, R.O.C.
(Received December 13, 2009; Accepted May 13, 2010)
In this study, we demonstrated a simple method that can be used to simultaneously modulate the far field pattern and enhance the light extraction of GaN-based light-emitting diodes (LEDs). In this method, microstructures were imprinted on a reliable spin-on-glass surface on top of a transparent conductive layer. The far-field pattern was modulated using microoptical structures, and at the same time, the light extraction was enhanced owing to the small refractive index difference and surface roughness. There was no decrease in the electrical performance of these devices. The peak intensity shifted from 0 to 22° in one-dimensional (1D) asymmetrically blazed periodic structures, and a flattened distribution with a uniform intensity within a span of 110° was observed in two-dimensional (2D) symmetrically periodic structures. This method achieved 13 and 40% light enhancements for 1D and 2D structures, respectively.
Key words: GaN, light-emitting diode (LED), imprinting technology, far-field pattern modulation, light extraction
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