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

doi:10.1364/OE.20.025058

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.

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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References

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Arif, R. A.
Bhat, J.
Bogdanov, M. V.
Bohn, E.
Bulashevich, K. A.
Chang, K. H.
Chen, C. P.
Chen, H. H.
Cheng, Y. W.
Choi, E. S.
Choi, H. W.
Collins, D.
Cook, L.
Craford, M. G.
David, A.
DenBaars, S.
Dpeck, J. D.
Ee, Y. K.
Evstratov, I. Yu.
Fink, A.
Fletcher, R.
Fu, Y. C.
Gardner, N.
Gilchrist, J. F.
Goetz, W.
Grillot, P.
Hao, X.
Harbers, G.
Horng, R. H.
Hsieh, M. Y.
Hu, E. L.
Huang, F. W.
Huang, J. J.
Huang, S. C.
Huang, S. H.
Huh, C.
Jang, S. J.
Kang, E. J.
Karpov, S. Yu.
Ke, M. Y.
Keuper, M.
Khare, R.
Khokhlev, O. V.
Kim, A.
Krames, M.
Kumnorkaew, P.
Lai, W. C.
Lee, K. S.
Lee, M. L.
Lee, Y. T.
Li, K. H.
Li, X. H.
Liu, S. P.
Liu, X.
Ludowise, M.
Lza, M.
Martin, P. S.
Matioli, E.
McGroddy, K.
Misra, M.
Mueller, G.
Mueller-Mach, R.
Nakamura, S.
Ou, S. L.
Pan, K. M.
Park, C. Y.
Park, G. C.
Park, S. J.
Peng, L. H.
Ramm, M. S.
Rudaz, S.
Shen, Y.-C.
Sheu, J. K.
Song, R.
Song, Y. M.
Steigerwald, D.
Steranka, F. M.
Stöber, W.
Stockman, S.
Subramanya, S.
Tansu, N.
Tong, H.
Trottier, T.
Tu, S. J.
Wang, C. Y.
Weisbuch, C.
Wierer, J. J.
Wu, H. M.
Wu, Y.
Wuu, D. S.
Xu, X.
Yang, C. C.
Yeh, Y. H.
Yin, Z.
Zhao, H.

Appl. Phys. Lett.

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]
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]

IEEE J. Sel. Top. Quantum Electron.

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]
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]

IEEE Photon. J.

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]

J. Appl. Phys.

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]
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]

J. Colloid Interface Sci.

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]

Nanotechnology

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]

Opt. Express

Phys. Status Solidi A

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]

Phys. Status Solidi C

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]

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