Abstract

We report on the improvement of light extraction efficiency from GaN-based light-emitting diodes (LEDs) using Ni1-xCoxO nanoparticles (NPs) formed on the p-GaN layer. After formation of Ni1-xCoxO hemispherical lens arrays on the blue LEDs by drop-casting colloidal NPs, electroluminescence (EL) and photoluminescence (PL) measurements are conducted to investigate the electrical and optical properties. The PL and EL intensities from the blue LEDs with the Ni1-xCoxO NPs are 1.74 and 1.61 times greater, respectively, than a conventional LED. Finally, a hybrid approach using ZnO nanorod arrays grown on the NiCoO hemispherical lens shows further increase of light extraction by 3.8 and 6.2 times compared to LEDs with bare NiCoO NPs and without any NPs, respectively. Finite-difference time-domain (FDTD) simulation results also agree well with the experimental results. The enhancement of light extraction from LEDs with ZnO nanorods and NiCoO NPs can be attributed to an enlarged escape angle cone and increased probability of light scattering.

© 2014 Optical Society of America

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  1. S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
    [CrossRef]
  2. S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
    [CrossRef]
  3. Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
    [CrossRef]
  4. 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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
    [CrossRef]
  5. S. H. Yeon and J. Park, “Enhancement of photoluminescence intensity of GaN-based light-emitting diodes with coated polystyrene/silica core-shell nanostructures,” J. Nanosci. Nanotechnol. 13(11), 7653–7657 (2013).
    [CrossRef] [PubMed]
  6. T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
    [CrossRef]
  7. M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
    [CrossRef]
  8. L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
    [CrossRef] [PubMed]
  9. F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
    [CrossRef]
  10. G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
    [CrossRef]
  11. K. Song and J. Park, “Effects of the growth pressure of a-plane InGaN/GaN multi-quantum wells on the optical performance of light-emitting diodes,” Semicond. Sci. Technol. 28(1), 015010 (2013).
    [CrossRef]
  12. C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
    [CrossRef]
  13. X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
    [CrossRef]
  14. L. H. Ai and J. Jiang, “Rapid synthesis of nanocrystalline Co3O4 by a microwave-assisted combustion method,” Powder Technol. 195(1), 11–14 (2009).
    [CrossRef]
  15. T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
    [CrossRef]
  16. C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
    [CrossRef]
  17. J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
    [CrossRef]
  18. M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
    [CrossRef]
  19. Z. Yin, X. Liu, H. Wang, Y. Wu, X. Hao, Z. Ji, and X. Xu, “Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes,” Opt. Express 21(23), 28531–28542 (2013).
    [CrossRef] [PubMed]
  20. Y. H. Ko and J. S. Yu, “Urchin-aggregation inspired closely-packed hierarchical ZnO nanostructures for efficient light scattering,” Opt. Express 19(27), 25935–25943 (2011).
    [CrossRef] [PubMed]
  21. Z. Yin, X. Liu, H. Wang, Y. Wu, X. Hao, Z. Ji, and X. Xu, “Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes,” Opt. Express 21(23), 28531–28542 (2013).
    [CrossRef] [PubMed]

2013 (6)

S. H. Yeon and J. Park, “Enhancement of photoluminescence intensity of GaN-based light-emitting diodes with coated polystyrene/silica core-shell nanostructures,” J. Nanosci. Nanotechnol. 13(11), 7653–7657 (2013).
[CrossRef] [PubMed]

T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
[CrossRef]

G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
[CrossRef]

K. Song and J. Park, “Effects of the growth pressure of a-plane InGaN/GaN multi-quantum wells on the optical performance of light-emitting diodes,” Semicond. Sci. Technol. 28(1), 015010 (2013).
[CrossRef]

Z. Yin, X. Liu, H. Wang, Y. Wu, X. Hao, Z. Ji, and X. Xu, “Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes,” Opt. Express 21(23), 28531–28542 (2013).
[CrossRef] [PubMed]

Z. Yin, X. Liu, H. Wang, Y. Wu, X. Hao, Z. Ji, and X. Xu, “Light transmission enhancement from hybrid ZnO micro-mesh and nanorod arrays with application to GaN-based light-emitting diodes,” Opt. Express 21(23), 28531–28542 (2013).
[CrossRef] [PubMed]

2012 (1)

Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
[CrossRef]

2011 (2)

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Y. H. Ko and J. S. Yu, “Urchin-aggregation inspired closely-packed hierarchical ZnO nanostructures for efficient light scattering,” Opt. Express 19(27), 25935–25943 (2011).
[CrossRef] [PubMed]

2009 (2)

L. H. Ai and J. Jiang, “Rapid synthesis of nanocrystalline Co3O4 by a microwave-assisted combustion method,” Powder Technol. 195(1), 11–14 (2009).
[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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

2008 (2)

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
[CrossRef]

2007 (1)

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

2006 (1)

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

2005 (2)

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

2001 (2)

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
[CrossRef]

1995 (1)

S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
[CrossRef]

1994 (1)

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
[CrossRef]

Ai, L. H.

L. H. Ai and J. Jiang, “Rapid synthesis of nanocrystalline Co3O4 by a microwave-assisted combustion method,” Powder Technol. 195(1), 11–14 (2009).
[CrossRef]

Arif, R. A.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Calin, G.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Chen, P. C.

M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
[CrossRef]

Choi, H. W.

Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
[CrossRef]

Dobromir, M.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Doroftei, C.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Ee, Y. K.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Engelhard, M. H.

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

Exarhos, G. J.

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
[CrossRef]

Fan, Z. Y.

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

Ferris, K. F.

C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
[CrossRef]

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

Gilchrist, J. F.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Goldberger, J.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Greene, L. E.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Hao, X.

Ho, C. L.

M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
[CrossRef]

Iacomi, F.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Iftimie, N.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Irimia, M.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Jang, Y. H.

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

Ji, Z.

Jiang, H. X.

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

Jiang, J.

L. H. Ai and J. Jiang, “Rapid synthesis of nanocrystalline Co3O4 by a microwave-assisted combustion method,” Powder Technol. 195(1), 11–14 (2009).
[CrossRef]

Jung, G. Y.

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

Jung, K. Y.

T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
[CrossRef]

Khizar, M.

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

Kim, D. H.

G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
[CrossRef]

Kim, H. S.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Kim, J. K.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Kim, K. H.

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

Kim, S. M.

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

Kim, T. S.

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

Ko, Y. H.

Kumar, G. M.

G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
[CrossRef]

Kumnorkaew, P.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Law, M.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Lee, M. K.

M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
[CrossRef]

Li, K. H.

Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
[CrossRef]

Li, X.

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

Li, Z.

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

Lin, J. Y.

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

Liu, X.

Meyaard, D.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Mohammad, S. N.

S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
[CrossRef]

Mont, F. W.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Montano, M.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Morkoç, H.

S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
[CrossRef]

Mukai, T.

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
[CrossRef]

Nakamura, S.

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
[CrossRef]

Noemaun, A. N.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Park, J.

G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
[CrossRef]

K. Song and J. Park, “Effects of the growth pressure of a-plane InGaN/GaN multi-quantum wells on the optical performance of light-emitting diodes,” Semicond. Sci. Technol. 28(1), 015010 (2013).
[CrossRef]

S. H. Yeon and J. Park, “Enhancement of photoluminescence intensity of GaN-based light-emitting diodes with coated polystyrene/silica core-shell nanostructures,” J. Nanosci. Nanotechnol. 13(11), 7653–7657 (2013).
[CrossRef] [PubMed]

T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
[CrossRef]

Park, Y. J.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Poxson, D. J.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Qian, Y.

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

Rusu, G. G.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Salvador, A. A.

S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
[CrossRef]

Sandu, A. V.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Scarlat, C.

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

Schubert, E. F.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Senoh, M.

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
[CrossRef]

Somorjai, G.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Son, T.

T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
[CrossRef]

Sone, C.

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

Song, K.

K. Song and J. Park, “Effects of the growth pressure of a-plane InGaN/GaN multi-quantum wells on the optical performance of light-emitting diodes,” Semicond. Sci. Technol. 28(1), 015010 (2013).
[CrossRef]

Stewart, D. C.

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

Tan, D. H.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Tansu, N.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Tong, H.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Wang, H.

Windisch, C. F.

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
[CrossRef]

Wu, Y.

Xu, X.

Yang, P.

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Yeon, S. H.

S. H. Yeon and J. Park, “Enhancement of photoluminescence intensity of GaN-based light-emitting diodes with coated polystyrene/silica core-shell nanostructures,” J. Nanosci. Nanotechnol. 13(11), 7653–7657 (2013).
[CrossRef] [PubMed]

Yin, Z.

Yu, J. S.

Zhang, Q.

Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
[CrossRef]

Zhang, X.

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

Zhao, H.

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

Appl. Phys. Lett. (5)

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double heterostructure blue light emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994).
[CrossRef]

Q. Zhang, K. H. Li, and H. W. Choi, “InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography,” Appl. Phys. Lett. 100(6), 061120 (2012).
[CrossRef]

M. Khizar, Z. Y. Fan, K. H. Kim, J. Y. Lin, and H. X. Jiang, “Nitride deep-ultraviolet light-emitting diodes with microlens array,” Appl. Phys. Lett. 86(17), 173504 (2005).
[CrossRef]

J. K. Kim, A. N. Noemaun, F. W. Mont, D. Meyaard, E. F. Schubert, D. J. Poxson, H. S. Kim, C. Sone, and Y. J. Park, “Elimination of total internal reflection in GaInN light-emitting diodes by graded refractive-index micropillars,” Appl. Phys. Lett. 93(22), 221111 (2008).
[CrossRef]

T. S. Kim, S. M. Kim, Y. H. Jang, and G. Y. Jung, “Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography,” Appl. Phys. Lett. 91(17), 171114 (2007).
[CrossRef]

CrystEngComm (1)

G. M. Kumar, D. H. Kim, and J. Park, “Colloidal Ni1-xCoxO nanostructures as anodic buffer layers in hybrid polypyrrole/Zn1-yInyO p–n junctions,” CrystEngComm 15(40), 8195–8201 (2013).
[CrossRef]

Curr. Appl. Phys. (1)

T. Son, K. Y. Jung, and J. Park, “Enhancement of the light extraction of GaN-based green light emitting diodes via nanohybrid structures,” Curr. Appl. Phys. 13(6), 1042–1045 (2013).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

M. K. Lee, C. L. Ho, and P. C. Chen, “Light extraction efficiency enhancement of GaN blue LED by liquid-phase-deposited ZnO Rods,” IEEE Photon. Technol. Lett. 20(4), 252–254 (2008).
[CrossRef]

J. Nanosci. Nanotechnol. (1)

S. H. Yeon and J. Park, “Enhancement of photoluminescence intensity of GaN-based light-emitting diodes with coated polystyrene/silica core-shell nanostructures,” J. Nanosci. Nanotechnol. 13(11), 7653–7657 (2013).
[CrossRef] [PubMed]

J. Select. Topics Quantum Electron. (1)

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,” J. Select. Topics Quantum Electron. 15(4), 1218–1225 (2009).
[CrossRef]

J. Vac. Sci. Technol. (1)

C. F. Windisch, K. F. Ferris, and G. J. Exarhos, “Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films,” J. Vac. Sci. Technol. 19(4), 1647–1651 (2001).
[CrossRef]

Nano Lett. (1)

L. E. Greene, M. Law, D. H. Tan, M. Montano, J. Goldberger, G. Somorjai, and P. Yang, “General route to vertical ZnO nanowire arrays using textured ZnO seeds,” Nano Lett. 5(7), 1231–1236 (2005).
[CrossRef] [PubMed]

Opt. Express (3)

Powder Technol. (1)

L. H. Ai and J. Jiang, “Rapid synthesis of nanocrystalline Co3O4 by a microwave-assisted combustion method,” Powder Technol. 195(1), 11–14 (2009).
[CrossRef]

Proc. IEEE (1)

S. N. Mohammad, A. A. Salvador, and H. Morkoç, “Emerging gallium nitride based devices,” Proc. IEEE 83(10), 1306–1355 (1995).
[CrossRef]

Semicond. Sci. Technol. (1)

K. Song and J. Park, “Effects of the growth pressure of a-plane InGaN/GaN multi-quantum wells on the optical performance of light-emitting diodes,” Semicond. Sci. Technol. 28(1), 015010 (2013).
[CrossRef]

Solid State Commun. (1)

X. Li, X. Zhang, Z. Li, and Y. Qian, “Synthesis and characteristics of NiO nanoparticles by thermal decomposition of nickel dimethylglyoximate rods,” Solid State Commun. 137(11), 581–584 (2006).
[CrossRef]

Thin Solid Films (2)

C. F. Windisch, G. J. Exarhos, K. F. Ferris, M. H. Engelhard, and D. C. Stewart, “Infrared transparent spinel films with p-type conductivity,” Thin Solid Films 398-399, 45–52 (2001).
[CrossRef]

F. Iacomi, G. Calin, C. Scarlat, M. Irimia, C. Doroftei, M. Dobromir, G. G. Rusu, N. Iftimie, and A. V. Sandu, “Functional properties of nickel cobalt oxide thin films,” Thin Solid Films 520(1), 651–655 (2011).
[CrossRef]

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Figures (8)

Fig. 1
Fig. 1

Schematic diagram of fabricated blue LED structures with ZnO nanorod arrays on Ni1-xCoxO hemisphere lenses.

Fig. 2
Fig. 2

(a) Powder XRD patterns and plane indices of the A(NiO) and B(Co3O4) phase in Ni1-xCoxO NPs. (b) TEM images of the Ni1-xCoxO NPs at low magnification (left) and high magnification (right)

Fig. 3
Fig. 3

UV-Vis absorbance spectrum of the colloidal Ni1-xCoxO dispersions in solvent.

Fig. 4
Fig. 4

(a) SEM image of Ni1-xCoxO hemisphere lens coated on top of p-GaN. (b) The histogram for the diameter distribution of hemispherical NiCoO NPs.

Fig. 5
Fig. 5

SEM images obtained from the ZnO nanorod arrays on(5(a) and 5 (c)) a conventional LED and (5(b) and 5(d)) a NiCoO NP/LED. (c) and (d) show magnified SEM images for 5(a) and 5(b), respectively.

Fig. 6
Fig. 6

The PL spectra of the LEDs with (red line) and without (black line) NiCoO hemisphere lens formed on top of p-GaN .

Fig. 7
Fig. 7

EL spectra obtained from blue LEDs with different surface nanostructures at an injection current of 50mA.

Fig. 8
Fig. 8

FDTD simulation results for light extraction characteristics as a function of various different nanostructures.

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