Abstract

We investigate the effects of the refractive index of the encapsulant on the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) for GaN LEDs (n ≈ 2.5) and AlGaInP LEDs (n ≈ 3.0). For non-absorbing rectangular parallelepiped LED chips, as the refractive index of the encapsulant increases, the LEE first increases quasi-linearly, then increases sub-linearly, and finally a saturation is reached. Furthermore, LEDs with a dual-layer graded-refractive-index (GRIN) encapsulant (n encapsulant1 = 1.57 and n encapsulant2 = 1.41) is fabricated through a two-step curing process. We demonstrate that such an LED further enhances the LEE by reducing Fresnel reflection loss at the encapsulant/air interface by 35% compared with an LED encapsulated with a single-layer encapsulant (n encapsulant = 1.57).

© 2011 OSA

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References

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  1. E. F. Schubert, Light-Emitting Diodes, 2nd ed. (Cambridge University Press, 2006).
  2. S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
    [CrossRef]
  3. T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
    [CrossRef]
  4. J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
    [CrossRef]
  5. E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
    [CrossRef]
  6. J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
    [CrossRef]
  7. X. H. Wang, W. Y. Fu, P. T. Lai, and H. W. Choi, “Evaluation of InGaN/GaN light-emitting diodes of circular geometry,” Opt. Express 17(25), 22311–22319 (2009).
    [CrossRef] [PubMed]
  8. J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
    [CrossRef]
  9. C. H. Chiu, P. Yu, C. H. Chang, C. S. Yang, M. H. Hsu, H. C. Kuo, and M. A. Tsai, “Oblique electron-beam evaporation of distinctive indium-tin-oxide nanorods for enhanced light extraction from InGaN/GaN light emitting diodes,” Opt. Express 17(23), 21250–21256 (2009).
    [CrossRef] [PubMed]
  10. F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
    [CrossRef]
  11. H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
    [CrossRef]
  12. I. Moreno, D. Bermúdez, and M. Avendaño-Alejo, “Light-emitting diode spherical packages: an equation for the light transmission efficiency,” Appl. Opt. 49(1), 12–20 (2010).
    [CrossRef] [PubMed]
  13. Z. Liu, K. Wang, X. Luo, and S. Liu, “Precise optical modeling of blue light-emitting diodes by Monte Carlo ray-tracing,” Opt. Express 18(9), 9398–9412 (2010).
    [CrossRef] [PubMed]

2011

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

2010

2009

C. H. Chiu, P. Yu, C. H. Chang, C. S. Yang, M. H. Hsu, H. C. Kuo, and M. A. Tsai, “Oblique electron-beam evaporation of distinctive indium-tin-oxide nanorods for enhanced light extraction from InGaN/GaN light emitting diodes,” Opt. Express 17(23), 21250–21256 (2009).
[CrossRef] [PubMed]

X. H. Wang, W. Y. Fu, P. T. Lai, and H. W. Choi, “Evaluation of InGaN/GaN light-emitting diodes of circular geometry,” Opt. Express 17(25), 22311–22319 (2009).
[CrossRef] [PubMed]

J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
[CrossRef]

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

2008

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

2005

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

2004

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Avendaño-Alejo, M.

Bermúdez, D.

Chang, C. H.

Chhajed, S.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

Chiu, C. H.

Cho, J.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Choi, H. W.

Crawford, M. H.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

David, A.

J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
[CrossRef]

DenBaars, S. P.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Fischer, A. J.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

Fleury, B.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Fu, W. Y.

Fujii, T.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Gao, Y.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Hayashi, H.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Hsu, M. H.

Hu, E.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Hu, E. L.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Iza, M.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Kim, H.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Kim, J. K.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

Kuo, H. C.

Kurai, S.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Lai, P. T.

Lee, J. W.

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Lee, W.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

Liu, S.

Liu, Z.

Luo, X.

Matioli, E.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Megens, M. M.

J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
[CrossRef]

Mont, F. W.

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

Moreno, I.

Nakamura, S.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Park, Y.

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Pfaff, N.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Rangel, E.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Schubert, E. F.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

Schubert, M. F.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

Sharma, R.

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

Siegel, R. W.

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

Sone, C.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Speck, J.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Taguchi, T.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Takeshita, J.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Tsai, M. A.

Uchida, Y.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Wang, K.

Wang, X. H.

Weisbuch, C.

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

Wierer, J. J.

J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
[CrossRef]

Yang, C. S.

Yoon, E.

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Yoon, S.

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Yu, P.

Adv. Mater.

J. K. Kim, S. Chhajed, M. F. Schubert, E. F. Schubert, A. J. Fischer, M. H. Crawford, J. Cho, H. Kim, and C. Sone, “Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact,” Adv. Mater. 20(4), 801–804 (2008).
[CrossRef]

Appl. Opt.

Appl. Phys. Lett.

S. Chhajed, W. Lee, J. Cho, E. F. Schubert, and J. K. Kim, “Strong light extraction enhancement in GaInN light-emitting diodes by using self-organized nanoscale patterning of p-type GaN,” Appl. Phys. Lett. 98(7), 071102 (2011).
[CrossRef]

T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening,” Appl. Phys. Lett. 84(6), 855 (2004).
[CrossRef]

E. Matioli, E. Rangel, M. Iza, B. Fleury, N. Pfaff, J. Speck, E. Hu, and C. Weisbuch, “High extraction efficiency light-emitting diodes based on embedded air-gap photonic-crystals,” Appl. Phys. Lett. 96(3), 031108 (2010).
[CrossRef]

J. Appl. Phys.

F. W. Mont, J. K. Kim, M. F. Schubert, E. F. Schubert, and R. W. Siegel, “High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes,” J. Appl. Phys. 103(8), 083120 (2008).
[CrossRef]

J. Light Vis. Env.

H. Hayashi, J. Takeshita, Y. Uchida, S. Kurai, and T. Taguchi, “Dependence of the light extraction from near-ultraviolet light-emitting diodes on refraction index, transmittance and shape,” J. Light Vis. Env. 33(3), 137–141 (2009).
[CrossRef]

Nat. Photonics

J. J. Wierer, A. David, and M. M. Megens, “III-nitride photonic-crystal light-emitting diodes with high extraction efficiency,” Nat. Photonics 3(3), 163–169 (2009).
[CrossRef]

Opt. Express

Phys. Stat. Solidi C

J. Cho, H. Kim, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate,” Phys. Stat. Solidi C 2(7), 2874–2877 (2005).
[CrossRef]

Other

E. F. Schubert, Light-Emitting Diodes, 2nd ed. (Cambridge University Press, 2006).

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Figures (4)

Fig. 1
Fig. 1

Analytical calculation of the LEE as a function of the refractive index of the encapsulant for GaN LEDs and AlGaInP LEDs.

Fig. 2
Fig. 2

(a) The numerically calculated LEE as a function of θ C at the semiconductor/encapsulant interface for a non-absorbing rectangular parallelepiped LED. (b) Numerical calculation results and the 3D ray-tracing simulation results of the LEE as a function of the refractive index of the encapsulant for GaN LEDs. (c) Numerical calculation results and the 3D ray-tracing simulation results of the LEE as a function of the refractive index of the encapsulant for AlGaInP LEDs.

Fig. 3
Fig. 3

Comparison between the measured LOP and the 3D ray-tracing simulated LEE as a function of the refractive index of the encapsulant for GaN LEDs and AlGaInP LEDs.

Fig. 4
Fig. 4

Measured LOP as a function of the refractive index of the encapsulant for unencapsulated AlGaInP LED chips, AlGaInP LEDs encapsulated with encapsulants having different refractive indices (n encapsulant = 1.41 and 1.57), and AlGaInP LEDs encapsulated with a dual-layer GRIN encapsulant (n encapsulant1 = 1.57 and n encapsulant2 = 1.41). The inset shows the schematic diagram of a fabricated AlGaInP LED encapsulated with a dual-layer GRIN encapsulant.

Equations (1)

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η LEE(encapsulated) = 1 cos θ C,   encapsulant 1 cos θ C,   air η LEE(unencapsulated)                                                                 = 1 cos ( arcsin n encapsulant n semiconductor ) 1 cos ( arcsin 1 n semiconductor ) η LEE(unencapsulated)

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