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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 14 — Jul. 2, 2012
  • pp: 15997–16002

Micro/nano structures induced by femtosecond laser to enhance light extraction of GaN-based LEDs

Tien-Li Chang, Zhao-Chi Chen, and Yeeu-Chang Lee  »View Author Affiliations

Optics Express, Vol. 20, Issue 14, pp. 15997-16002 (2012)

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Surface texturing has been widely adopted to enhance the light extraction efficiency of light-emitting diodes (LEDs), and chemical etching is a technique commonly used to produce surface texturing. This study employed femtosecond lasers to apply ITO films directly onto the surface of LEDs to generate periodic micro/nanostructures and roughen the surface without contact or chemical substances. As a result, photons emitted in the active region escape into the free space, due to the scattering effect produced by texturing. This study discovered that light-emitting efficiency increases with surface roughness, and achieved an improvement of 18%. Caution regarding laser fluence was required during laser processing to avoid damaging the LED beneath the ITO film, which could detract from the electrical characteristics.

© 2012 OSA

OCIS Codes
(220.4000) Optical design and fabrication : Microstructure fabrication
(230.3670) Optical devices : Light-emitting diodes
(320.2250) Ultrafast optics : Femtosecond phenomena
(220.4241) Optical design and fabrication : Nanostructure fabrication

ToC Category:
Optical Devices

Original Manuscript: May 10, 2012
Revised Manuscript: June 8, 2012
Manuscript Accepted: June 20, 2012
Published: June 28, 2012

Tien-Li Chang, Zhao-Chi Chen, and Yeeu-Chang Lee, "Micro/nano structures induced by femtosecond laser to enhance light extraction of GaN-based LEDs," Opt. Express 20, 15997-16002 (2012)

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  1. Y.-H. Sun, Y.-W. Cheng, S.-C. Wang, Y.-Y. Huang, C.-H. Chang, S.-C. Yang, L.-Y. Chen, M.-Y. Ke, C.-K. Li, Y.-R. Wu, and J. J. Huang, “Optical properties of the partially strain relaxed InGaN/GaN light-emitting diodes induced by p-type GaN surface texturing,” IEEE Electron Device Lett.32(2), 182–184 (2011). [CrossRef]
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  8. X. C. Wang, G. C. Lim, F. L. Ng, W. Liu, and S. J. Chua, “Femtosecond pulsed laser-induced periodic surface structures on GaN/sapphire,” Appl. Surf. Sci.252(5), 1492–1497 (2005). [CrossRef]
  9. T. H. R. Crawford and H. K. Haugen, “Sub-wavelength surface structures on silicon irradiated by femtosecond laser pulses at 1300 and 2100 nm wavelengths,” Appl. Surf. Sci.253(11), 4970–4977 (2007). [CrossRef]
  10. C. W. Cheng, W. C. Shen, C. Y. Lin, Y. J. Lee, and J. S. Chen, “Fabrication of micro/nano crystalline ITO structures by femtosecond laser pulses,” Appl. Phys., A Mater. Sci. Process.101(2), 243–248 (2010). [CrossRef]
  11. W. C. Peng and Y. C. S. Wu, “Enhanced light output in double roughened GaN light-emitting diodes via various texturing treatments of undoped-GaN layer,” Jpn. J. Appl. Phys.45(10A), 7709–7712 (2006). [CrossRef]

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