OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 22 — Oct. 22, 2012
  • pp: 25058–25063

Light-extraction enhancement and directional emission control of GaN-based LEDs by self-assembled monolayer of silica spheres

Hee Kwan Lee, Yeong Hwan Ko, Ganji Seeta Rama Raju, and Jae Su Yu  »View Author Affiliations

Optics Express, Vol. 20, Issue 22, pp. 25058-25063 (2012)

View Full Text Article

Enhanced HTML    Acrobat PDF (1119 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



The light extraction of 1 × 1 mm2 GaN-based blue light-emitting diodes (LEDs) was enhanced by a self-assembled monolayer (SAM) of silica submicron spheres. The silica spheres were synthesized with various spherical sizes via the ammonia-catalyzed hydrolysis and condensation of tetraethyl orthosilicate in water/ethanol solutions. Hexagonal closely-packed (HCP) silica sphere monolayer was formed onto the indium tin oxide layer of the LED by a spin coating process. The size effect of silica spheres on the light-extraction efficiency (LEE) of GaN-based LEDs was theoretically studied and their optimum size was determined. The simulation results showed that the use of silica spheres can improve the LEE by 1.1-1.32 times compared to the conventional LEDs. The light output power of the LED with 650-nm-thick SAM of HCP silica spheres was experimentally enhanced by 1.28 and 1.23 times under the injection currents of 100 and 350 mA, respectively. By employing the SAM of HCP silica spheres, the directional emission pattern was relatively converged, indicating a reasonable consistency with the simulation result.

© 2012 OSA

OCIS Codes
(220.2740) Optical design and fabrication : Geometric optical design
(230.3670) Optical devices : Light-emitting diodes
(310.1210) Thin films : Antireflection coatings
(220.4241) Optical design and fabrication : Nanostructure fabrication

ToC Category:
Optical Design and Fabrication

Original Manuscript: May 7, 2012
Revised Manuscript: August 29, 2012
Manuscript Accepted: October 9, 2012
Published: October 18, 2012

Hee Kwan Lee, Yeong Hwan Ko, Ganji Seeta Rama Raju, and Jae Su Yu, "Light-extraction enhancement and directional emission control of GaN-based LEDs by self-assembled monolayer of silica spheres," Opt. Express 20, 25058-25063 (2012)

Sort:  Author  |  Year  |  Journal  |  Reset  


  1. F. M. Steranka, J. Bhat, D. Collins, L. Cook, M. G. Craford, R. Fletcher, N. Gardner, P. Grillot, W. Goetz, M. Keuper, R. Khare, A. Kim, M. Krames, G. Harbers, M. Ludowise, P. S. Martin, M. Misra, G. Mueller, R. Mueller-Mach, S. Rudaz, Y.-C. Shen, D. Steigerwald, S. Stockman, S. Subramanya, T. Trottier, and J. J. Wierer, “High power LEDs - Technology status and market applications,” Phys. Status Solidi A194(2), 380–388 (2002). [CrossRef]
  2. R. H. Horng, S. H. Huang, C. C. Yang, and D. S. Wuu, “Efficiency improvement of GaN-based LEDs with ITO texturing window layers using natural lithography,” IEEE J. Sel. Top. Quantum Electron.12(6), 1196–1201 (2006). [CrossRef]
  3. C. Huh, K. S. Lee, E. J. Kang, and S. J. Park, “Improved light-output and electrical performance of InGaN-based light emitting diode by microroughening of the p-GaN surface,” J. Appl. Phys.93(11), 9383–9385 (2003). [CrossRef]
  4. Y. M. Song, E. S. Choi, G. C. Park, C. Y. Park, S. J. Jang, and Y. T. Lee, “Disordered antireflective nanostructures on GaN-based light-emitting diodes using Ag nanoparticles for improved light extraction efficiency,” Appl. Phys. Lett.97(9), 093110 (2010). [CrossRef]
  5. S. L. Ou, D. S. Wuu, S. P. Liu, Y. C. Fu, S. C. Huang, and R. H. Horng, “Pulsed laser deposition of ITO/AZO transparent contact layers for GaN LED applications,” Opt. Express19(17), 16244–16251 (2011). [CrossRef] [PubMed]
  6. Z. Yin, X. Liu, Y. Wu, X. Hao, and X. Xu, “Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays,” Opt. Express20(2), 1013–1021 (2012). [CrossRef] [PubMed]
  7. S. J. Tu, J. K. Sheu, M. L. Lee, C. C. Yang, K. H. Chang, Y. H. Yeh, F. W. Huang, and W. C. Lai, “Enhanced output power of GaN-based LEDs with embedded AlGaN pyramidal shells,” Opt. Express19(13), 12719–12726 (2011). [CrossRef] [PubMed]
  8. K. McGroddy, A. David, E. Matioli, M. Lza, S. Nakamura, S. DenBaars, J. D. Dpeck, C. Weisbuch, and E. L. Hu, “Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes,” Appl. Phys. Lett.93(10), 103502 (2008). [CrossRef]
  9. K. H. Li and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide photonic crystal current-spreading layer,” J. Appl. Phys.110(5), 053104 (2011). [CrossRef]
  10. Y. W. Cheng, K. M. Pan, C. Y. Wang, H. H. Chen, M. Y. Ke, C. P. Chen, M. Y. Hsieh, H. M. Wu, L. H. Peng, and J. J. Huang, “Enhanced light collection of GaN light emitting devices by redirecting the lateral emission using nanorod reflectors,” Nanotechnology20(3), 035202 (2009). [CrossRef] [PubMed]
  11. Y. K. Ee, P. Kumnorkaew, R. A. Arif, H. Tong, H. Zhao, J. F. Gilchrist, and N. Tansu, “Optimization of light extraction efficiency of III-nitride LEDs with self-assembled colloidal-based microlenses,” IEEE J. Sel. Top. Quantum Electron.15(4), 1218–1225 (2009). [CrossRef]
  12. X. H. Li, R. Song, Y. K. Ee, P. Kumnorkaew, J. F. Gilchrist, and N. Tansu, “Light extraction efficiency and radiation patterns of III-nitride light-emitting diodes with colloidal microlens arrays with various aspect ratios,” IEEE Photon. J.3(3), 489–499 (2011). [CrossRef]
  13. M. V. Bogdanov, K. A. Bulashevich, O. V. Khokhlev, I. Yu. Evstratov, M. S. Ramm, and S. Yu. Karpov, “Effect of ITO spreading layer on performance of blue light-emitting diodes,” Phys. Status Solidi C7(7–8), 2127–2129 (2010). [CrossRef]
  14. W. Stöber, A. Fink, and E. Bohn, “Controlled growth of monodisperse silica spheres in the micron size range,” J. Colloid Interface Sci.26(1), 62–69 (1968). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


Fig. 1 Fig. 2 Fig. 3
Fig. 4 Fig. 5

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited