Abstract
The improvement in light extraction efficiency (LEE) of GaN-based LEDs is one of the most important areas for increasing the external quantum efficiency for solid-state lighting applications. We summarize the advances in this field. GaN-based light-emitting diodes (LEDs) have made a lot of progress with regard to growth, doping, and p-ohmic contacts [1–3]. The external quantum efficiency (EQE) of LEDs is equal to IQE (internal quantum efficiency) ×LEE (light extraction efficiency). Although the internal quantum efficiency (IQE) has been improved by advances in epitaxial growth techniques, the methods used to extract the photons from the quantum wells (QWs) still need to be improved. It has been reported that the LEE has to be over 90% to achieve 200 lm/W in white LEDs.According to Snell’s law, the light extraction angle (escape angle or escape cone) between GaN (n ∼ 2. 5) and air (n ∼ 1) was about 23. 5∘. Snell’s law states that the escape angle (θ) can be calculated by \(\theta {=\sin }^{-1}({n}_{\mathrm{air}}/{n}_{\mathrm{GaN}})\) where n air and n GaN are the index of air and GaN, respectively. Therefore, the total internal reflection (TIR) resulting from the narrow escape cone prevents the protons from escaping from the semiconductor. In other applications such as optical fibers and optical waveguides, TIR is required. If Indium tin oxide, which is a common transparent conducting oxide (n ∼ 2. 19), is used, the escape angle can be increased up to 27∘, which is still narrow. The photons outside of the escape angle will be re-absorbed after multiple reflections or increase the operating temperature by dissipation (Fig. 5.1).
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
S. Nakamura, G. Fasol, S. Pearton, The Blue Laser Diode: The Complete Story/Edition 2, (Springer Berlin, 2000)
E.F. Schubert, J.K. Kim, Science, 308, 1274 (2005)
M. Fukuda, Optical Semiconductor Devices, (Wiley, New York, 1999)
I. Schnitzer, E. Yablonovitch, C. Caneau, T.J. Gmitter, A. Scherer, Appl. Phys. Lett. 63(16), 2174 (1993)
T. Fujii, Y. Gao, R. Sharma, E.L. Hu, S.P DenBaars, S. Nakamura, Appl. Phys. Lett. 84, 855 (2004)
Younghun Jung, Kwang Hyeon Baik, Fan Ren, Stephen J. Pearton, Jihyun Kim, J. Electrochem. Soc., 157(6), H676–H678 (2010)
D. Li, M. Sumiya, S. Fuke, D. Yang, D. Que, Y. Suzuki, Y. Fukuda, J. Appl. Phys. 90, 4219 (2001)
H.M. Ng, N.G. Weimann, A. Chowdhury, J. Appl. Phys. 94, 650 (2003)
Younghun Jung, Jihyun Kim, Soohwan Jang, Kwang Hyeon Baik, Yong Gon Seo, Sung-Min Hwang, Opt. Exp. Vol. 18, No.9, pp. 9728–9732 (2010)
C.H. Chiu, T.C. Lu, H.W. Huang, C.F. Lai, C.C. Kao, J.T. Chu, C.C. Yu, H.C. Kuo, S.C. Wang, C.F. Lin, T.H. Hsueh, Nanotechnology 18, 445201 (2007)
X. Qian, J. Li, D. Wasserman, W.D. Goodhue, Appl. Phys. Lett. 93, 231907 (2008)
W. Stöber, A. Fink, E.J. Bohn, Colloid Interface Sci., 26, 62 (1968)
Y. Li, W. Cai, G. Duan, Chem. Mater., 20, 615 (2008)
Ching-Mei Hsu, Stephen T. Connor, Mary X. Tang, Yi Cui, Appl. Phys. Lett. 93, 133109 (2008)
Wai Yuen Fu, Kenneth Kin-Yip Wong, H.W. Choi, Appl Phys Lett 95, 133125 (2009)
Yan-Kuin Su, Jian-Jhong Chen, Chuing-Liang Lin, Shi-Ming Chen Wen-Liang Li, Chien-Chih Kao, Jpn J Appl Phys., 47(8), 6706 (2008)
B.J. Kim, H. Jung, S.H. Kim, J. Bang, J. Kim, IEEE Photonics Technol. Lett., Vol. 21, pp.700–7002 (2009)
Se Gyu Jang, Dae-Geun Choi, Chul-Joon Heo, Su Yeon Lee, Seung-Man Yang, Adv. Mater. 20, 4862 (2008)
B.E.A. Saleh, M.C. Teich, Fundamentals of Photonics, 2nd (Wiley-Interscience, 2006)
J.K. Kim, S. Chhajed, M.F. Schubert, E.F. Schubert, A.J. Fischer, M.H. Crawford, J. Cho, H. Kim, C. Sone, Adv. Mater., 20, 801 (2008)
J.J. Wierer, A. David, M.M. Megens, Nat. Photonics, 3, 163 (2009)
A. David, H. Benisty, C. Weisbuch, J. Display Tech., 3, 133 (2007)
J.S. Biteen, D. Pacifici, N.S. Lewis, H.A. Atwaer, Nano Lett. 5, 1768 (2005)
K. Okamoto, I. Niki, A. Shvartser, Y. Narukawa, T. Mukai, A. Scherer, Nat. Mater. 3, 601 (2004)
K. Okamoto, I. Niki, A. Scherer, Y. Narukawa, T. Mukai, Y. Kawakami, Appl. Phys. Lett., 87, 071102 (2005)
M.-K. Kwon, J.-Y. Kim, B.-K. Kim, I.-K. Park, C.-Y. Cho, C.C. Byeon, S.-J. Park, Adv. Mater., 20, 1253 (2008)
C.E. Lee, H.C. Kuo, Y.C. Lee, M.R. Tsai, T.C. Lu, S.C. Wang, C.T. Kuo, IEEE Photon. Technol. Lett., 20 (3), 184 (2008)
C.-C. Kao, H.-C. Kuo, H.-W. Huang, J.-T. Chu, Y.-C. Peng, Y.-L. Hsieh, C.Y. Luo, S.-C. Wang, C.-C. Yu, C.-F. Lin, IEEE Photon. Technol. Lett., 17 (1), 19, (2005)
C.S. Chang, S.J. Chang, Y.K. Su, C.T. Lee, Y.C. Lin, W.C. Lai, S.C. Shei, J.C. Ke, H.M. Lo, IEEE Photon. Technol. Lett., 16 (3), 750, (2004)
M. Yamada, T. Mitani, Y. Narukawa, S. Shioji, I. Niki, S. Sonobe, K. Deguchi, M. Sano T. Mukai, Jpn. J. Appl. Phys., 41, L1431 (2002)
K. Tadatomo, H. Okagawa, Y. Ohuchi, T. Tsunekawa, T. Jyouichi, Y. Imada, M. Kato, H. Kudo, T. Taguchi, Phys. Stat. Sol. (a) 188(1), 121–125 (2001)
Acknowledgements
The research at Korea University was supported by the Carbon Dioxide Reduction and Sequestration Center, one of the twenty-first Century Frontier R&D Program funded by the Ministry of Education, Science and Technology of Korea.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2012 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Kim, J. (2012). Improved Light Extraction Efficiency in GaN-Based Light Emitting Diodes. In: Pearton, S. (eds) GaN and ZnO-based Materials and Devices. Springer Series in Materials Science, vol 156. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-23521-4_5
Download citation
DOI: https://doi.org/10.1007/978-3-642-23521-4_5
Published:
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-23520-7
Online ISBN: 978-3-642-23521-4
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)