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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)
http://dx.doi.org/10.1364/OE.20.025058


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Abstract

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

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

Citation
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)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-22-25058


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