Abstract

The light extraction efficiency of GaN-based LEDs as a function of the position of the light source over the active layer is studied. Several parameters, including chip dimensions, absorption coefficients and package are analyzed on the basis of a Monte-Carlo ray tracing simulation. The light extraction efficiency of a Thin-GaN LED is studied with respect to a sapphire-based LED, including the surface texture.

© 2005 Optical Society of America

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References

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  1. A. Zukauskas, M. S. Shur, and R. Caska, Introduction to Solid-state Lighting, (John Wiley & Sons, New York, 2002).
  2. Daniel A. Steigerwald, Jerome C. Bhat, Dave Collins, Robert M. Fletcher, Mari Ochiai Holcomb, Michael J. Ludowise, Paul S. Martin, and Serge L. Rudaz, �??Illumination with solid state lighting technology,�?? IEEE J. Select. Topics Quantum Electron. 8, 310, (2002).
    [CrossRef]
  3. M. R. Krames, M. Ochiai-Holcomb, G. E. Hofler, C. Carter-Coman, E. I. Chen, I.-H. Tan, P. Grillot, N. F. Gardner, H. C. Chui, J-W. Huang, S.A. Stockman, F. A. Kish, and M. G. Craford, �??High-power truncated-pyramid (Al0.5 Ga 1 - x )0.5 In0.5 P/GaP light-emitting diodes exhibiting >50% external quantum efficiency,�?? Appl. Phys. Lett. 75, 2365 (1999).
    [CrossRef]
  4. X. Guo, Y.-L. Li, and E. F. Schubert, �??Efficiency of GaN/InGaN light-emitting diodes with interdigitated mesa geometry,�?? Appl. Phys. Lett. 79, 1936 (2001).
    [CrossRef]
  5. 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,�?? Appl. Phys. Lett. 93, 9383 (2003).
  6. T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. Danbaars, and S. Nakamura, �??Increase in the extraction efficiency of GaN-base light emitting diodes via surface roughening,�?? Appl. Phys. Lett. 84, 855 (2004).
    [CrossRef]
  7. Y. Gao, T. Fujii, R. Sharma, K. Fujito, S. P. Danbaars and S. Nakamura, �??Roughening Hexagonal surface morphology on Laser lift-off (LLO) N face GaN with simple photo-enhanced chemical wet etching,�?? Jap. J. Appl. Phys. 43, 637, (2004).
    [CrossRef]
  8. C. C. Sun, C. Y. Lin, T. X. Lee, and T. H. Yang, �??Enhancement of light extraction of GaN-based LED with introducing micro-structure array, �?? Opt. Eng. 43, 1700 (2004).
    [CrossRef]
  9. S. J. Lee, �??Analysis of light-emitting diode by Monte Carlo photo simulation,�?? Appl. Opt. 40, 1427 (2001).
    [CrossRef]
  10. <a href="http://www.osram-os.com/.">http://www.osram-os.com/.</a>

Appl. Opt.

Appl. Phys. Lett.

M. R. Krames, M. Ochiai-Holcomb, G. E. Hofler, C. Carter-Coman, E. I. Chen, I.-H. Tan, P. Grillot, N. F. Gardner, H. C. Chui, J-W. Huang, S.A. Stockman, F. A. Kish, and M. G. Craford, �??High-power truncated-pyramid (Al0.5 Ga 1 - x )0.5 In0.5 P/GaP light-emitting diodes exhibiting >50% external quantum efficiency,�?? Appl. Phys. Lett. 75, 2365 (1999).
[CrossRef]

X. Guo, Y.-L. Li, and E. F. Schubert, �??Efficiency of GaN/InGaN light-emitting diodes with interdigitated mesa geometry,�?? Appl. Phys. Lett. 79, 1936 (2001).
[CrossRef]

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,�?? Appl. Phys. Lett. 93, 9383 (2003).

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

IEEE J. Select. Topics Quantum Electron.

Daniel A. Steigerwald, Jerome C. Bhat, Dave Collins, Robert M. Fletcher, Mari Ochiai Holcomb, Michael J. Ludowise, Paul S. Martin, and Serge L. Rudaz, �??Illumination with solid state lighting technology,�?? IEEE J. Select. Topics Quantum Electron. 8, 310, (2002).
[CrossRef]

Jap. J. Appl. Phys.

Y. Gao, T. Fujii, R. Sharma, K. Fujito, S. P. Danbaars and S. Nakamura, �??Roughening Hexagonal surface morphology on Laser lift-off (LLO) N face GaN with simple photo-enhanced chemical wet etching,�?? Jap. J. Appl. Phys. 43, 637, (2004).
[CrossRef]

Opt. Eng.

C. C. Sun, C. Y. Lin, T. X. Lee, and T. H. Yang, �??Enhancement of light extraction of GaN-based LED with introducing micro-structure array, �?? Opt. Eng. 43, 1700 (2004).
[CrossRef]

Other

<a href="http://www.osram-os.com/.">http://www.osram-os.com/.</a>

A. Zukauskas, M. S. Shur, and R. Caska, Introduction to Solid-state Lighting, (John Wiley & Sons, New York, 2002).

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Figures (6)

Fig. 1.
Fig. 1.

LEE vs. absorption coefficient of the active layer for the point sources in three different positions.

Fig. 2.
Fig. 2.

LEE vs. chip dimensions for center and corner point sources.

Fig. 3.
Fig. 3.

LEE vs. absorption coefficient of the active layer on different faces of the LED.

Fig. 4.
Fig. 4.

A comparison of the LEEs of sapphire-based and Thin-GaN LEDs with different absorption coefficients. The blue and orange bars indicate the LEE from the top surface and other surfaces, respectively. Both of the LEDs are coated with reflective film with a reflectivity of A, 100%; B, 85%; and C, 75%.

Fig. 5.
Fig. 5.

Four types of LEDs with different surface textures, the upper ones represent sapphire-based LEDs and the lower ones are Thin-GaN LEDs.

Fig. 6.
Fig. 6.

A comparison of the LEEs for the four cases.

Tables (1)

Tables Icon

Table 1. Parameters of each layer in the simulated LED.

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