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Proceedings Paper

Top transmission grating GaN LED simulations for light extraction improvement
Author(s): Simeon Trieu; Xiaomin Jin; Ashton Ellaboudy; Bei Zhang; Xiang-Ning Kang; Guo-Yi Zhang; Xiong Chang; Wei Wei; Sun Yong Jian; Fu Xing Xing
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Paper Abstract

We study the top transmission grating's improvement on GaN LED light extraction efficiency. We use the finite difference time domain (FDTD) method, a computational electromagnetic solution to Maxwell's equations, to measure light extraction efficiency improvements of the various grating structures. Also, since FDTD can freely define materials for any layer or shape, we choose three particular materials to represent our transmission grating: 1) non-lossy p-GaN, 2) lossy indium tin oxide (ITO), and 3) non-lossy ITO (α=0). We define a regular spacing between unit cells in a crystal lattice arrangement by employing the following three parameters: grating cell period (Α), grating cell height (d), and grating cell width (w). The conical grating model and the cylindrical grating model are studied. We also presented in the paper directly comparison with reflection grating results. Both studies show that the top grating has better performance, improving light extraction efficiency by 165%, compared to that of the bottom reflection grating (112%), and top-bottom grating (42%). We also find that when grating cells closely pack together, a transmission grating maximizes light extraction efficiency. This points our research towards a more closely packed structure, such as a 3-fold symmetric photonic crystal structure with triangular symmetry and also smaller feature sizes in the nano-scale, such as the wavelength of light at 460 nm, half-wavelengths, quarter wavelengths, etc.

Paper Details

Date Published: 21 February 2011
PDF: 11 pages
Proc. SPIE 7933, Physics and Simulation of Optoelectronic Devices XIX, 79331Y (21 February 2011); doi: 10.1117/12.871595
Show Author Affiliations
Simeon Trieu, California Polytechnic State Univ., San Luis Obispo (United States)
Peking Univ. (China)
Xiaomin Jin, California Polytechnic State Univ., San Luis Obispo (United States)
Peking Univ. (China)
Ashton Ellaboudy, California Polytechnic State Univ., San Luis Obispo (United States)
Bei Zhang, Peking Univ. (China)
Xiang-Ning Kang, Peking Univ. (China)
Guo-Yi Zhang, Peking Univ. (China)
Xiong Chang, Peking Univ. (China)
Wei Wei, Peking Univ. (China)
Sun Yong Jian, Peking Univ. (China)
Fu Xing Xing, Peking Univ. (China)

Published in SPIE Proceedings Vol. 7933:
Physics and Simulation of Optoelectronic Devices XIX
Bernd Witzigmann; Fritz Henneberger; Yasuhiko Arakawa; Alexandre Freundlich, Editor(s)

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