Shi Cao, Sheng Huang, Yinghan Wu
Beijing 21st Century International School, Beijing, China
Light-emitting diodes (LED) have attracted people’s attention due to their special features such as low power consumption and high durability. At the same time, their low-carbon, energy-saving, and environmental protection features, make LED frequently applied in areas such as display, photos, and optical communications. With the acceleration of the development of solid-state photo technology, LED has become the most promising environmentally friendly lighting source to be used widely. However, due to the physical properties of GaN-based materials, the low light extraction rate severely limits the sustainable development of LEDs. As a result, how to improve the light extraction efficiency (LEE) of LEDs is one of the most important research in the field of solid-state lighting. One of the reasons for the relatively low LEE comes from the phenomenon of total internal reflection inside the chip, resulting in photon absorption and loss of capacitance, which greatly reduces the LEE of GaN-based LEDs. This paper mainly summarizes the methods of patterning the titanium layer, patterning/roughening Indium-tin Oxide (ITO) transparent electrode layer, patterning sapphire substrate, special-shaped chip, back shadow, photonic crystal, and stealth cutting to capture high LEE of the LEDs.
Light-emitting diodes, GaN-based materials, Light extraction efficiency, Total internal reflection
Shi Cao, Sheng Huang, Yinghan Wu. Study on light extraction of nitride LED. Academic Journal of Materials & Chemistry (2023) Vol. 4, Issue 6: 43-47. https://doi.org/10.25236/AJMC.2023.040608.
 Wuu D. S., Wang W. K., Wen K. S., Huang S. C., Lin S. H., Horng R. H., Yu Y. S., Pan M. H. Fabrication of pyramidal patterned sapphire substrates for high-efficiency InGaN-based light emitting diodes. Journal of The Electrochemical Society, 2006, 153(8): 765-770.
 Chen Jian, Li Xiaoli, Li Haihua, Wang Qingkang, Research of LED light extraction efficiency of photonic crystal with square and hexagonal lattice. Acta Physica Sinica, 2009, 58(9): 6216-6221.
 Lin Wenyu, Wuu Dong Sing, Huang, Shih Cheng, Horng, Ray Hua, Enhanced Output Power of Near-Ultraviolet InGaN/AlGaN LEDs with Patterned Distributed Bragg Reflectors. IEEE Transactions On Electron Devices, 2010, 58(1): 173-179.
 Lee, Yeeu-Chang, Ni, Ching-Huai, Chen, Chih-Yeeu, Enhancing light extraction mechanisms of GaN-based light-emitting diodes through the integration of imprinting microstructures, patterned sapphire substrates, and surface roughness. Optics Express, 2010, 18(23): 489-498.
 Huang, Shaohua, HorngRay Hua, Wen, Kuo Sheng, Lin, Yi-Feng, Yen, Kuo Wei; Wuu Dong Sing, Improved light extraction of nitride-based flip-chip light-emitting diodes via sapphire shaping and texturing. Ieee Photonics Technology Letters, 2006, 18(21-24), 2623-2625.
 Chen Yixin, Zheng Wanhua, Chen Wei, Chen Lianghui, Tang Yidan, Shen Guangdi, AlGalnP LED with surface structure of two-dimensional photonic crystal. Acta Physics Sinica, 2010, 59(11): 8083-8087.
 Yin Zihao, Wang Qingkang. A Theoretical Research of Photonic Crystal Structural Geometry Designing on LED Output Efficiency. Acta Sinica QuantumOptica, 2009, 15(4): 358-363.
 Wang P, Gan Z, and Liu S. Improved light extraction of GaN-based light-emitting diodes with surface-patterned ITO. Opt Laser Technol, 2009, 41(2): 823-826
 Chang S J, Shen C F, and Chen w S. Nitride-based light emitting diodes with indium tin oxide electrode patterned by imprint lithography. Appl Phys Lett, 2007, 91(1): 013504-1-3
 Byeon K J, Hong E J, Park H, et al. Enhancement of the photon extraction of green andblue LEDs by patterning the indium tin oxide top layer. Semicond Sci Tech, 2009, 24(10): 105004-1-5
 Krames M, Holcomb M, and Collins D. High-power truncated-inverted-pyramid (AlxGa1-x) 0. 5In0. 5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency. Appl Phys Lett, 1999, 75(16): 2365-2367
 Hui K N, Hui K S, Lee H, et al. Enhanced light output of angled sidewall light-emitting diodes with reflective silver films. Thin Solid Films, 2011, 519(8): 2504-2507
 Hsueh T H, Sheu J K, Huang H W, et al. Enhancement in light output of InGaN-based microhole array light-emitting diodes. IEEE Photon Tech Lett, 2005, 17(6): 1163-1165
 Lee J S, Lee J, Kim S, et al. Fabrication of reflective GaN mesa sidewalls for the application to high extraction efficiency LEDs. Phys Status Solidi C, 2007, 4(7): 2625-2628
 Lee J S, Lee J, Kim S, et al. GaN light-emitting diode with deep-angled mesa sidewalls for enhanced light emission in the surface-normal direction. IEEE Tran Electron Dev, 2008, 55(2): 523-526
 Chang C S, Chang S J, Lee C T, et al. Nitride-based LEDs with textured side walls. IEEE Photon Tech Lett, 2004, 16(3): 750-752
 Kao C C, Kuo H C, Huang H w, et al. Light-output enhancement in a Nitride-based light-emitting diode with 22° undercut sidewalls. IEEE Photon Tech Lett, 2005, 17(1): 19-21
 Tan LX, Li J, Liu S. A light emitting diode's chip structure with low stress and high light extraction efficiency. The 58th Electronic Components and Technology Conference, 2008: 783-788
 Liuxi Tan, Jia Li, Zongyuan Liu, et al. A Light Emitting Diode's Chip Structure with Low Stress and High Light Extraction Efficiency[C]. //58th Electronic Components & Technology Conference (ECTC 2008), vol. 2.: 783-788.
 Zhang Xianpeng, Han Yanjun, Luo Yi et al. GaN based blue LED with p-GaN surface microstructure etched by ICP . Semiconductor Optoelectronics, 2008(01): 6-9+15. DOI: 10. 16818/ j. ssn1001-5868. 2008. 01. 002.
 Reiner Windisch, Rainer Butendeich, Stefan Illek, et al. 100-lm/W InGaAlP Thin-Film Light- Emitting Diodes With Buried Microreflectors. IEEE Photonics Technology Letters, 2007, 19(10): 774-776.
 Zhang Jianming, Zou Deshu, Liu Sinan et al. New omnidirectional reflection AlGa- indium- phosphorus thin film light-emitting diodes. Acta Physica Sinica, 2007(05): 2905-2909.
 T. N. Oder, K. H. Kim, J. Y. Lin, et al. III-nitride blue and ultraviolet photonic crystal light emitting diodes. Applied physics letters, 2004, 84(4): 466-468.
 J. J. Wierer, M. R. Krames, J. E. Epler, et al. InGaN/GaN quantum-well heterostructure light-emitting diodes employing photonic crystal structures. Applied physics letters, 2004, 84(19): 3885-3887.
 Dong Ho Kim, Chi O Cho, Yeong Geun Roh, et al. Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns. Applied physics letters, 2005, 87(20): 203508-1-203508-3-0.
 T. A. Truong, L. M. Campos, E. Matioli, et al. Light extraction from GaN-based light emitting diode structures with a noninvasive two-dimensional photonic crystal. Applied physics letters, 2009, 94(2): 023101-1-023101-3-0.
 Wierer J, David A, Megens M. III-nitride photonic-crystal light-emitting diodes with high extraction efficiency. Nature photonics, 2009(3): 3.
 Hu Haiyang, Xu Xingsheng, Lu Lin et al. Improvement of light output efficiency of photonic crystal GaN LED by conventional process. Photoelectronics. Laser, 2008(05): 569-572.
 LEE, J, KIM, DH, KIM, J, et al. GaN-based light-emitting diodes directly grown on sapphire substrate with holographically generated two-dimensional photonic crystal patterns. Current applied physics: the official journal of the Korean Physical Society, 2009, 9(3): 633-635. DOI: 10. 1016/j. cap. 2008. 05. 020.
 Fan Sh, Villeneuve Pr, Joannopoulos Jd, et al. High extraction efficiency of spontaneous emission from slabs of photonic crystals. Physical review letters, 1997, 78(17): 3294-3297.
 Lin C H, Lai C F, Ko T S, et al. Enhancement of InGaN–GaN Indium–Tin–Oxide Flip-Chip Light-Emitting Diodes With TiO$_2$–SiO$_2$Multilayer Stack Omnidirectional Reflector. IEEE Photonics Technology Letters, 2006, 18(19): 2050-2052. DOI: 10. 1109/lpt. 2006. 883330.
 Bao Kui, Zhang Bei, Dai Tao, et al. Improving the output light intensity of GAN-based light-emitting Diodes by Microstructure printing . Chinese Journal of Semiconductors, 2007.