氧化物微纳米结构提高GaN基LED光提取效率的研究
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摘要
发光二极管(Light-emitting diodes,LED)是目前最具前景的固态光源,被广泛应用于多个领域。获得高效率高亮度LED的关键在于提高LED外量子效率,LED外量子效率由内量子效率和光提取效率的乘积决定。目前,LED内量子效率已经较高(大于70%),但是低的光提取效率严重限制了LED的外量子效率。通过增加光提取效率来提高LED的外量子效率已成为当前的一个研究热点。
本论文以提高GaN基LED的光提取效率为研究目标,通过在LED出光面设计和制备氧化锌(ZnO)纳米结构阵列、ZnO微纳复合结构和二氧化钛(TiO2)微米簇来提高GaN基LED的光提取效率,并对其光学和电学性能进行深入研究,主要研究内容如下：
1、研究了ZnO纳米结构的几何形状对光提取效率的影响,并制备了ZnO纳米结构阵列提高LED的光提取效率。运用几何光学方法分析得到等腰三角形比矩形的光提取效率高的结论,推广到三维情况,提出锥比棒的光提取效率高的推论。通过水溶液沉积法在LED的氧化铟锡(ITO)电流扩展层上生长了ZnO纳米棒阵列,LED的光功率提高了约60%；调节生长条件制备了ZnO纳米锥阵列,LED的光功率提高了约110%。理论和实验结果都表明ZnO纳米锥阵列比ZnO纳米棒阵列能更有效地提高LED的光提取效率。
2、利用模板法和水溶液沉积法在石英玻璃上制备了ZnO微米网孔和纳米棒复合结构,研究了其入射角度分辨的光透过特性,以此为指导,在LED表面制备了两种ZnO微纳复合结构,提高了LED的光提取效率,探讨了微纳复合结构的光提取增强机制。实验结果表明,在宏观上ZnO微米网孔的二维衍射光栅作用和ZnO纳米棒阵列的光散射作用可以协同增强光从高折射率材料到空气的透过率。ZnO微米网孔和纳米棒复合结构提高了LED的光功率95.9%,共聚焦扫描电致发光显微成像在微观上表明ZnO微米网孔和纳米棒复合结构能集成ZnO微米网孔孔壁侧面出光作用和ZnO纳米棒阵列光散射作用；ZnO微米柱和纳米棒复合结构提高了LED的光功率86.4%,ZnO微米柱和纳米棒复合结构能集成ZnO微米柱侧面出光作用和ZnO纳米棒光散射作用。
3、设计和制备了嵌入式周期排列TiO2微米簇,提高了LED的光提取效率,深入研究了TiO2微米簇的光提取增强机制。首先设计了一种将TiO2微米簇周期性嵌入在ITO和p-GaN之间的LED结构模型,期望能够同时利用TiO2微米簇增强光提取以及利用ITO保持电流扩展获得高性能LED。在实验上通过模板法和酸热法制备了嵌入式六方排列TiO2微米簇LED和嵌入式四方排列TiO2微米簇,LED电学性能保持良好。嵌入式六方排列TiO2微米簇能增加LED光功率171.1%,结合蓝宝石衬底粗化能增加LED光功率225.3%。封装后嵌入式六方排列TiO2微米簇+衬底粗化LED比封装空白LED的光功率增加82.1%。光学显微成像和共聚焦扫描电致发光显微成像直观地显示了TiO2微米簇的光提取增强作用,TiO2微米簇的导光和光散射作用是提高LED光提取效率的主要原因。超低温PL光谱测试显示嵌入式六方排列TiO2微米簇结合粗化衬底将封装后LED的绝对光提取效率从45.8%提高到71.4%。实验结果证明,周期性嵌入式TiO2微米簇的结构设计兼顾了TiO2微纳米结构的高光提取效率的优点以及LED的良好电学性能和有源区稳定高效发光的优点。
At present, light-emitting diode (LED) is the most promising solid-state light source, which has been widely used in plenty of fields. High efficiency and high brightness LEDs depend on high external quantum efficiency that relies on the arithmetic product of internal quantum efficiency and light extraction efficiency. Currently, LEDs have high internal quantum efficiency (greater than70%), but low light extraction efficiency severely restricts the external quantum efficiency. Therefore, improving the light extraction efficiency to enable high external quantum efficiency of LEDs has become a hot research field.
In this paper, the main work was focused on improving light extraction efficiency of GaN-based LEDs. Zinc oxide (ZnO) nanorods/nanorones array, ZnO micro&nano composite structures and titanium dioxide (TiO2) microclusters were designed and fabricated to improve the light extraction efficiency of GaN-based LEDs. The main contents are as follows:
1. The influence of the geometry on light extraction efficiency was studied, and ZnO nanostructures arrays were used to improve the light extraction efficiency of LEDs. It was proved that light extraction efficiency of isosceles triangle is higher than that of rectangular by geometrical optics method. Extending to three-dimensional case, an assumption that light extraction efficiency of cone was higher than that of rod was the proposed. ZnO nanorods array was grown on indium tin oxide (ITO) of LEDs by aqueous deposition method. Light output power of LEDs is improved by about60%. ZnO nanocones array was prepared by regulating growth condition. Light output power of LEDs with ZnO nanocones array is increased by110%. Theoretical and experimental results show that ZnO nanocones array enable higher light extraction enhancement of LEDs than ZnO nanorods array.
2. Hybrid ZnO micro-mesh&nanorod arrays was designed on quartz glass by templates and solution deposition, and incident angle-resolved light transmission was studied. Two kinds of ZnO micro&nano composite structures were fabricated to improve light extraction efficiency of LEDs, and light extraction enhancement mechanism was studied. Experimental results show that two-dimensional diffraction grating effect of ZnO micro-mesh and light scattering effect of ZnO nanorods array can synergistically enhanced the transmittance from a high refractive index material to air. Hybrid ZnO micro-mesh&nanorod arrays can improve light output power of LEDs by95.9%. Scanning confocal electroluminescence microscopy imaging shows hybrid ZnO micro-mesh&nanorod arrays can integrated light output from holes' side wall of ZnO micro-mesh and light scattering effect of ZnO nanorod. Hybrid ZnO micro-cylinders and nanorods array can increase light power of LEDs by86.4%. Confocal scanning electroluminescence microscopy imaging shows it can integrate light output from side walls of ZnO micro-cylinders and light scattering effect of ZnO nanorods.
3. Embedded patterned TiO2microclusters were designed and prepared to improve light extraction efficiency of LEDs, and light extraction enhancement mechanism of TiO2microclusters was studied. Firstly, a new LED structure with TiO2microclusters periodically embedded between ITO and p-GaN was designed. Secondly, in experiment LEDs with embedded hexagonal and square arranged TiO2microclusters were prepared, and the electrical properties of LEDs maintained good. Embedded hexagonal arranged TiO2microclusters can increase light output power of LEDs by171.1%, Embedded hexagonal arranged TiO2microclusters combining with roughened sapphire substrate can increase light output power of LEDs by225.3%. The light output power of encapsulated LEDs with embedded hexagonal arranged TiO2microclusters is greater than that of encapsulated blank LEDs by82.1%. Optical microscopic imaging and confocal scanning electroluminescence microscopic imaging visualize light extraction enhancement of TiO2microclusters. Light-guide and light-scattering effect of TiO2microclusters are the main reasons for light extraction efficiency enhancement of LEDs. Ultra-low temperature PL spectra measurement shows embedded hexagonal and square arranged TiO2microclusters combined with roughened sapphire substrate can increase the absolute light extraction efficiency of encapsulated LEDs from45.8%to71.4%. Experimental results show that the structural design of embedded patterned TiO2microclusters capably the high light extraction efficiency advantages of TiO2micro&nano structures, as well as good electrical properties of LEDs and high light-emitting efficiency of active region.
本论文以提高GaN基LED的光提取效率为研究目标,通过在LED出光面设计和制备氧化锌(ZnO)纳米结构阵列、ZnO微纳复合结构和二氧化钛(TiO2)微米簇来提高GaN基LED的光提取效率,并对其光学和电学性能进行深入研究,主要研究内容如下：
1、研究了ZnO纳米结构的几何形状对光提取效率的影响,并制备了ZnO纳米结构阵列提高LED的光提取效率。运用几何光学方法分析得到等腰三角形比矩形的光提取效率高的结论,推广到三维情况,提出锥比棒的光提取效率高的推论。通过水溶液沉积法在LED的氧化铟锡(ITO)电流扩展层上生长了ZnO纳米棒阵列,LED的光功率提高了约60%；调节生长条件制备了ZnO纳米锥阵列,LED的光功率提高了约110%。理论和实验结果都表明ZnO纳米锥阵列比ZnO纳米棒阵列能更有效地提高LED的光提取效率。
2、利用模板法和水溶液沉积法在石英玻璃上制备了ZnO微米网孔和纳米棒复合结构,研究了其入射角度分辨的光透过特性,以此为指导,在LED表面制备了两种ZnO微纳复合结构,提高了LED的光提取效率,探讨了微纳复合结构的光提取增强机制。实验结果表明,在宏观上ZnO微米网孔的二维衍射光栅作用和ZnO纳米棒阵列的光散射作用可以协同增强光从高折射率材料到空气的透过率。ZnO微米网孔和纳米棒复合结构提高了LED的光功率95.9%,共聚焦扫描电致发光显微成像在微观上表明ZnO微米网孔和纳米棒复合结构能集成ZnO微米网孔孔壁侧面出光作用和ZnO纳米棒阵列光散射作用；ZnO微米柱和纳米棒复合结构提高了LED的光功率86.4%,ZnO微米柱和纳米棒复合结构能集成ZnO微米柱侧面出光作用和ZnO纳米棒光散射作用。
3、设计和制备了嵌入式周期排列TiO2微米簇,提高了LED的光提取效率,深入研究了TiO2微米簇的光提取增强机制。首先设计了一种将TiO2微米簇周期性嵌入在ITO和p-GaN之间的LED结构模型,期望能够同时利用TiO2微米簇增强光提取以及利用ITO保持电流扩展获得高性能LED。在实验上通过模板法和酸热法制备了嵌入式六方排列TiO2微米簇LED和嵌入式四方排列TiO2微米簇,LED电学性能保持良好。嵌入式六方排列TiO2微米簇能增加LED光功率171.1%,结合蓝宝石衬底粗化能增加LED光功率225.3%。封装后嵌入式六方排列TiO2微米簇+衬底粗化LED比封装空白LED的光功率增加82.1%。光学显微成像和共聚焦扫描电致发光显微成像直观地显示了TiO2微米簇的光提取增强作用,TiO2微米簇的导光和光散射作用是提高LED光提取效率的主要原因。超低温PL光谱测试显示嵌入式六方排列TiO2微米簇结合粗化衬底将封装后LED的绝对光提取效率从45.8%提高到71.4%。实验结果证明,周期性嵌入式TiO2微米簇的结构设计兼顾了TiO2微纳米结构的高光提取效率的优点以及LED的良好电学性能和有源区稳定高效发光的优点。
At present, light-emitting diode (LED) is the most promising solid-state light source, which has been widely used in plenty of fields. High efficiency and high brightness LEDs depend on high external quantum efficiency that relies on the arithmetic product of internal quantum efficiency and light extraction efficiency. Currently, LEDs have high internal quantum efficiency (greater than70%), but low light extraction efficiency severely restricts the external quantum efficiency. Therefore, improving the light extraction efficiency to enable high external quantum efficiency of LEDs has become a hot research field.
In this paper, the main work was focused on improving light extraction efficiency of GaN-based LEDs. Zinc oxide (ZnO) nanorods/nanorones array, ZnO micro&nano composite structures and titanium dioxide (TiO2) microclusters were designed and fabricated to improve the light extraction efficiency of GaN-based LEDs. The main contents are as follows:
1. The influence of the geometry on light extraction efficiency was studied, and ZnO nanostructures arrays were used to improve the light extraction efficiency of LEDs. It was proved that light extraction efficiency of isosceles triangle is higher than that of rectangular by geometrical optics method. Extending to three-dimensional case, an assumption that light extraction efficiency of cone was higher than that of rod was the proposed. ZnO nanorods array was grown on indium tin oxide (ITO) of LEDs by aqueous deposition method. Light output power of LEDs is improved by about60%. ZnO nanocones array was prepared by regulating growth condition. Light output power of LEDs with ZnO nanocones array is increased by110%. Theoretical and experimental results show that ZnO nanocones array enable higher light extraction enhancement of LEDs than ZnO nanorods array.
2. Hybrid ZnO micro-mesh&nanorod arrays was designed on quartz glass by templates and solution deposition, and incident angle-resolved light transmission was studied. Two kinds of ZnO micro&nano composite structures were fabricated to improve light extraction efficiency of LEDs, and light extraction enhancement mechanism was studied. Experimental results show that two-dimensional diffraction grating effect of ZnO micro-mesh and light scattering effect of ZnO nanorods array can synergistically enhanced the transmittance from a high refractive index material to air. Hybrid ZnO micro-mesh&nanorod arrays can improve light output power of LEDs by95.9%. Scanning confocal electroluminescence microscopy imaging shows hybrid ZnO micro-mesh&nanorod arrays can integrated light output from holes' side wall of ZnO micro-mesh and light scattering effect of ZnO nanorod. Hybrid ZnO micro-cylinders and nanorods array can increase light power of LEDs by86.4%. Confocal scanning electroluminescence microscopy imaging shows it can integrate light output from side walls of ZnO micro-cylinders and light scattering effect of ZnO nanorods.
3. Embedded patterned TiO2microclusters were designed and prepared to improve light extraction efficiency of LEDs, and light extraction enhancement mechanism of TiO2microclusters was studied. Firstly, a new LED structure with TiO2microclusters periodically embedded between ITO and p-GaN was designed. Secondly, in experiment LEDs with embedded hexagonal and square arranged TiO2microclusters were prepared, and the electrical properties of LEDs maintained good. Embedded hexagonal arranged TiO2microclusters can increase light output power of LEDs by171.1%, Embedded hexagonal arranged TiO2microclusters combining with roughened sapphire substrate can increase light output power of LEDs by225.3%. The light output power of encapsulated LEDs with embedded hexagonal arranged TiO2microclusters is greater than that of encapsulated blank LEDs by82.1%. Optical microscopic imaging and confocal scanning electroluminescence microscopic imaging visualize light extraction enhancement of TiO2microclusters. Light-guide and light-scattering effect of TiO2microclusters are the main reasons for light extraction efficiency enhancement of LEDs. Ultra-low temperature PL spectra measurement shows embedded hexagonal and square arranged TiO2microclusters combined with roughened sapphire substrate can increase the absolute light extraction efficiency of encapsulated LEDs from45.8%to71.4%. Experimental results show that the structural design of embedded patterned TiO2microclusters capably the high light extraction efficiency advantages of TiO2micro&nano structures, as well as good electrical properties of LEDs and high light-emitting efficiency of active region.
引文
[1]H. J. Round, A Note on carborundum, Electrical World,1907,49,309-310.
[2]J. I. Pankove and M. J. Massoulie, Injection luminescence from gallium arsenide, Bull. Am. Phys. Soc.,1962,7,88.
[3]J. N. Holonyak and S. F. Bevacqua, Coherent (visible) light emission from Ga(ASI-xPx) junctions, Appl. Phys. Lett.,1962,1,82-83.
[4]S. Nakamura, M. Senoh and T. Mukai, P-GaN/N-InGaN/N-GaN double-hetero-structure blue-light-emitting diodes, Jpn. J. Appl. Phys.,1993,32, L8-L11.
[5]S. Nakamura and G. Fasol, The Blue Laser Diode:GaN based light emitters and lasers, Springer,1997,343.
[6]Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano and T. Mukai, White light emitting diodes with super-high luminous efficacy, J. Phys. D:Appl. Phys.,2010,43, 354002.
[7]http://www.led-professional.com/technology/light-generation/continues-to-push-the-boundaries-of-led-performance-by-breaking-300-lumens-per-watt-barrier
[8]毛兴武,张艳雯,周建军,祝大卫,新一代绿色光源LED及其应用技术,人民邮电出版社,2008,102.
[9]刘恩科,朱秉升,罗晋生,半导体物理学,国防工业出版社(第四版),2013,298-303.
[10]Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano and T. Mukai, White light emitting diodes with super-high luminous efficacy, J. Phys. D:Appl. Phys.,2010,43, 354002.
[11]T. Nakamura, M. Satoh, Schottky barrier height of a new ohmic contact NiSi2 to n-type 6H-SiC, Solid-State Electron.,2002,46,2063-2067.
[12]申屠伟进,胡飞,韩彦军,薛松,罗毅,钱可元,GaN基发光二极管芯片光提取效率的研究,光电子·激光,2005,16,385-389.
[13]E. F. Schubert, Light-Emitting Diodes,2nd ed. (Cambridge University,2006).
[14]P.C. Tsaia, W.R. Chen, Y.K. Su and C.Y. Huang, Enhanced light output of InGaN LEDs with a roughened p-GaN surface using different TMGa flow rates in p-AlGaN layer, Appl. Surf. Sci.,2010,256(22),6694-6698.
[15]A. David, Surface-Roughened Light-Emitting Diodes:An Accurate Model, J. Disp. Technol.,2013,9(5),301-316.
[16]X. F. Zeng, S. C. Shei and S. J. Chang, SiO2 Nanopillars on Microscale Roughened Surface of GaN-Based Light-Emitting Diodes by SILAR-Based Method, J. Nanomater.,2013(2013),753230.
[17]P.-W. Huang and Y. Sermon Wu, Output Power of AlGaInP Light Emitting Diode Improved by Double Roughening AlGaInP Surfaces, Electrochem. Solid-State Lett.,2010,13(5), H163-H165.
[18]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, J. Appl. Phys.,2003,93,9383-9385.
[19]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[20]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.,2004,84,855-857.
[21]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[22]X. Gao, X. Yan, X. Yao, L. Xu, K. Zhang, J. Zhang, B. Yang and L. Jiang, The dry-tyle antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography, Adv. Mater.,2007,19(17),2213-2217.
[23]Y. M. Song, G. C. Park, S. J. Jang, J. H. Ha, J. S. Yu and and Y. T. Lee, Multifunctional light escaping architecture inspired by compound eye surface structures:From understanding to experimental demonstration, Opt. Express,2011, 19(S2),A157-A165.
[24]K. Tadatomo, H. Okagawa, Y Ohuchi, T. Tsunekawa, Y Imada, M. Kato and T. Taguchi, High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy, Jpn. J. Appl. Phys.2001,40, L583-L585.
[25]H. Gao, F. Yan, Y. Zhang, J. Li, Y. Zeng and G. Wang, Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro- and nanoscale, J. Appl. Phys.,2008,103,014314.
[26]J.-H.Lee, D.-Y. Lee, B.-W. Oh and J.-H. Lee, Comparison of InGaN-Based LEDs . Grown on Conventional Sapphire and Cone-Shape-Patterned Sapphire Substrate, IEEE T. Electron Dev.,57(1),157-163.
[27]C.-F. Lin, C.-Min Lin, K.-T. Chen, W.-. Huang, M.-S. Lin, J.-J. Dai, R.-H. Jiang, Y.-C. Huang and C.-Y. Chang, Blue light-emitting diodes with a roughened backside fabricated by wet etching, Appl. Phys. Lett.,2009,95,201102.
[28]H. G. Kim, H. K. Kim, H.Y. Kim, H. Jeong, S. Chandramohan, P. Uthirakumar, M. S. Jeong, J.-S. Lee, E.-K. Suh and C.-H. Hong, Enhanced air-cavity effect of periodically oriented embedded air protrusions for high-efficiency InGaN/GaN light-emitting diodes, Opt. Letters,2010,35(18),3012-3014.
[29]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-inverted-pyramid (AlxGai-x)0.5Ino.5P/GaP light-emitting diodes exhibiting>50% external quantum efficiency, Appl. Phys. Lett.,1999,75,2365-2367.
[30]X. H. Wang, P. T. Lai and H. W. Choi, The contribution of sidewall light extraction to efficiencies of polygonal lightemitting diodes shaped with laser micromachining, J. Appl. Phys.,2010,108,023110.
[31]S. S. Schad, M. Scherer, M. Seyboth and V. Schwegler, Extraction efficiency of GaN-based LEDs, phys. stat. sol. (a),2001,188,127-130.
[32]E. Yablonovitch, Inhibited spontaneous emission in solid-state physics and electronics, Phys. Rev. Lett.,1987,58,2059-2062.
[33]S. John, Strong localization of photons in certain disordered dielectric superlattices, Phys. Rev. Lett.,1987,58,2486-2489.
[34]D.H.Kim, C.O.Cho, Y.G.Roh, H. Jeon, Y. S. Park, J. Cho, J. S. Im, C. Sone, Y. Park, W. J. Choi, Q. H. Park, Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns, Appl. Phys. Lett.,2005,87,203508-203510.
[35]E. Matioli and C. Weisbuch, Impact of photonic crystals on LED light extraction efficiency:approaches and limits to vertical structure designs, J. Phys. D:Appl. Phys.,2010,43,354005.
[36]G. Shambat, B. Ellis, J. Petykiewicz, M, A. Mayer, T. Sarmiento, J. Harris, E. E. Haller and J.Vuckovic, Nanobeam photonic crystal cavity light-emitting diodes, Appl. Phys. Lett.2011,99,071105.
[37]H.-Y.Ryu and J.-I. Shim, Structural Parameter Dependence of Light Extraction Efficiency in Photonic Crystal InGaN Vertical Light-Emitting Diode Structures, IEEE J. Quantum Elect.,2010,46(5),714-720.
[38]X. X Fu, B. Zhang, X. N. Kang, J. Deng, C. Xiong, T. Dai, X. Jiang, TongJun Yu, Z. Chen and G. Y. Zhang, GaN-based light-emitting diodes with photonic crystals structures fabricated by porous anodic alumina template, Opt. Express,2011, 19(S5),A1104-A1108.
[39]S. J. Chang, C. F. Shen, W. S. Chen, C. T. Kuo, T. K. Ko, S. C. Shei, J. K. Sheu, Nitride-based light emitting diodes with indium tin oxide electrode patterned by imprint lithography, Appl. Phys. Lett.,2007,91,013504.
[40]S. Fan, P. Villeneuve and J. D. Joannopoulos, High extraction efficiency of spontaneous emission from slabs of photonic crystals, Phys. Rev. Lett.,1997,78, 3294-3297.
[41]M. Boroditsky, R. Vrijen, T. F. Krauss, R. Coccioli and R. Bhat, E. Yablonovitch, Spontaneous emission extraction and Purcell enhancement from thin-film 2-D photonic crystals, J. Lightwave Technol,1999,17,2096-2112.
[42]M. Boroditsky, T. F. Krauss and R. Coccioli, Light extraction from optically pumped light-emitting diode by thin-slab photonic crystals, Appl. Phys. Lett.,1999, 75,1036-1038.
[43]A. Fehrembach, S. Enoch and A. Sentenac, Highly directive light sources using two-dimensional photonic crystal slabs, Appl. Phys. Lett.,2001,79,4280-4282.
[44]A. David, T. Fujii, R. Sharma, K. McGroddy, S. Nakamura, S. P. Denbaars, E. L. Hu, C. Weisbuch and H. Benisty, Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution, Appl. Phys. Lett.,2006,88,081124-081126.
[45]J. J. Wierer, A. David and M. M. Megens, Ⅲ-nitride photonic-crystal light-emitting diodes with high extraction efficiency, Nat. photonics,2009,3,163-169.
[46]T. Doan, C. Chu, C. Chen, W. Liu, J. Chu, J. Yeh, H. Chen, F. Fan and C. Tran, Vertical GaN based Light Emitting Diodes on metal alloy substrate for solid state lighting application, Proc. of SPIE,2006,6134,61340G-1-6.
[47]M. A. Tsai, P. Yu, C. L. Chao, C. H. Chiu, H. C. Kuo, S. H. Lin,J. J. Huang, T.C. Lu and S. C. Wang, Efficiency enhancement and beam shaping of GaN-InGaN vertical-injection light-emitting diodes via high-aspect-ratio nanorod arrays, IEEE Photonics Technol. Lett.,2009,21,257-259.
[48]J. O. Song, J. S. Kwak and T. Y. Seong, Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes, Appl. Phys. Lett.,2005,86,062103.
[49]K. Y. Ban, H. G. Hong, D. Y. Noh, J. I. Sohn, D. J. Kang and T. Y. Seong, Ir/Ag reflector for high-performance GaN-based near UV light emitting diodes, Mater. Sci. Eng. B,2006,133,26-29.
[50]J. Y. Kim, J. M. Lee and M. K. Kwon, Formation of low resistance and high reflectivity reflector on p-type GaN using Ni/Au/W/Ag ohmic contact, Solid state Lett.,2012,15, H198-H201.
[51]J. S. Ha, S. W. Lee, H. J. Lee, H. J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho and T. Yao, The fabrication of vertical light-emitting diodes using chemical lift-off process, IEEE Photonics Technol. Lett.,2008,20,175-177.
[52]W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romando and N. M. Johnson, InxGal-xN light emitting diodes on Si substrates fabricated by Pd-In metal bonding and laser lift-off, Appl. Phys. Lett.,2000,77, 2822-2824.
[53]J. J. Wierer, D. A. Steigerwald, M. R. Krames, J. J. O'Shea, M. J. Ludowise, G. Christenson, Y.-C. Shen, C. Lowery, P. S. Martin, S. Subramanya, W. Gotz, N. F. Gardner, R. S. Kern and S. A. Stockman, High-power AlGaInN flip-chip light-emitting diodes, Appl. Phys. Lett.,2001,78,3379-3381.
[54]S. J. Chang, W. S. Chen, S. C. Shei, C. F. Shen, T. K. Ko, J. M. Tsai, W. C. Lai, J. K. Sheu, A. J. Lin and S. C. Hung, GaN-Based power Flip-chip LEDs With Cu Submount, IEEE J. Sel. Top Quant.,2009,15(4),1287-1291.
[55]O. B. Shchekin, J. E. Epler, T. A. Trottier, T. Margalith, D. A. Steigerwald, M. O. Holcomb, P. S. Martin and M. R. Krames, High performance thin-film flip-chip InGaN-GaN light-emitting diodes, Appl. Phys. Lett.,2006,89(7),071109.
[56]J.-H. Lee, S.-M. Hwang, N.-S. Kim and J.-H. Lee, InGaN-Based High-Power Flip-Chip LEDs with Deep-Hole-Patterned Sapphire Substrate by Laser Direct Beam Drilling, IEEE Electr. Device L.,2010,31(7),698-700.
[57]S. H. Huang, R. H. Horng, K. S. Wen, Y. F. Lin, K.-W. Yen and D.-S. Wuu, Improved Light Extraction of Nitride-Based Flip-Chip Light-Emitting Diodes via Sapphire Shaping and Texturing, IEEE Photonics Technol. Lett.,2006,18(24), 2623-2625.
[58]R.-H.Horng, H.-L. Hu, M.-T. Chu, Y.-L. Tsai, Y.-J. Tsai, Ch.-P. Hsu and D.-S. Wuu, Performance of Flip-Chip Thin-Film GaN Light-Emitting Diodes With and without patterned Sapphire, IEEE Photonics Technol. Lett.,2010,22(8),550-552.
[59]J. M. Lee, J. Yi, W. W. Lee, H. Y. Jeong, T. Jung, Y. Kim and W. II Park, ZnO nanorods-graphene hybrid structures for enhanced current spreading and light extraction in GaN-based light emitting diodes, Appl. Phys. Lett.,2012,100, 061107.
[60]S.-Y. Jung and T.-Y. Seong, Improved light output power of GaN-based flip-chip light-emitting diode through SiO2 cones, Electro. Mater. Lett.,2012,8(6),549-552.
[61]C. L. Lin, P. H. Chen, Chia-Hua Chan, C. C. Lee, Chii-Chang Chen, Jeng-Yang Chang and C. Y. Liu, Light enhancement by the formation of an Al oxide honeycomb nanostructure on the n-GaN surface of thin-GaN light-emitting diodes, Appl. Phys. Lett.,2007,90(24),242106.
[62]T. S. Kim, S.-M. Kim, Y. H. Jan and G. Y. Jung, Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography, Appl. Phys. Lett.,2007,91,171114.
[63]J.-T. Lian, J.-H. Ye, J.-Y. Liou, K.-C. Tsao, N.-C. Chenb and T.-Y. Lin, Improved light extraction efficiency on GaN LEDs by an In2O3 nano-cone, J. Mater. Chem. C,2013,1,6559-6564.
[64]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, 2009,17(23),21250-21256.
[65]S. J. Wang, P. R. Wang, D. M. Kuo, H. R. Kuo and Ji.-S. Kuo, Improved light output of GaN-based vertical light emitting diodes using SiO2 nanotube arrays and transparent metal oxide current conduction layer, Appl. Phys. Lett.,2011,99, 131111.
[66]P. Uthirakumar, J. H. Kang, B. D. Ryu, H. G. Kim, H. K. Kim and C.-H. Hong, Nanoscale ITO/ZnO layer texturing for high-efficiency InGaN/GaN light emitting diodes, Mat. Sci. Eng. B,2010,166,230-234.
[67]Y.-C. Chao, C.-Y. Chen, C.-A. Lin, Y.-A. Dai and J.-H. He, Antireflection effect of ZnO nanorod arrays, J. Mater. Chem.,2010,20(37),8134-8138.
[68]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90,203515.
[69]S. J. An, J. H. Chae, G.-C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92,121108.
[70]K. S. Kim, S.-M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.
[71]H. Park, K.-J. Byeon, K.-Y. Yang, J.-Y. Cho and H. Lee, The fabrication of a patterned ZnO nanorod array for high brightness LEDs, Nanotechnology,2010, 21(35),355304.
[72]M.-S. Lin, C.-C. Chen, W.-C. Wang, C.-F. Lin and S.-Y. Chang, Fabrication of the selective-growth ZnO nanorods with a hole-array pattern on a p-type GaN:Mg layer through a chemical bath deposition process, Thin Solid Films,2010,518(24), 7398-7402.
[73]C. H. Chao, W. H. Lin, C. H. Chen, C. H. Changjean and C. F. Lin, Tunable Light extraction efficiency of GaN light emitting diodes by ZnO nanorod arrays. Semicond. Sci. Technol,2009,24,105017.
[74]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light Output Enhancement of GaN-based Light emitting Diodes Using ZnO nanorod Arrays Produced by Aqueous Solution Growth Technique, IEEE Photonics Technol. Lett., 2010,22(16),1220-1222.
[75]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chenb, Enhancement of Light Output Intensity by Integrating ZnO Nanorod Arrays on GaN-based LLO Vertical LEDs, Electrochem. Solid ST.,2008,11(4), H84-H87.
[76]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 Photonics Technol. Lett.,2008,20(4),252-254.
[77]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2008,94, 071118.
[78]X. Liu, W. Zhou, Z. Yin, X. Hao, Y. Wu and X. Xu, Growth of single-crystalline rutile TiO2 nanorod arrays on GaN light-emitting diodes with enhanced light extraction, J. Mater. Chem.,2012,22,3916-3921.
[79]M. Ma, J. Cho, E. F. Schubert, Y. Park, G. B. Kim and C. Sone, Strong light-extraction enhancement in GalnN light-emitting diodes patterned with TiO2 micro-pillars with tapered sidewalls, Appl. Phys. Lett.,2012,101,141105.
[80]K. M. Yoon, K. Y. Yang, K. J. Byeon and H. Lee, Enhancement of light extraction in GaN based LED structures using TiO2 nano-structures, Solid-State Electron., 2010,54,484-487.
[1]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, J. Appl. Phys.,2003,93,9383-9385.
[2]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[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.,2004,84,855-857.
[4]J. J. Wierer, A. David and M. M. Megens, Ⅲ-nitride photonic-crystal light-emitting diodes with high extraction efficiency, Nat. photonics,2009,3,163-169.
[5]J. O. Song, J. S. Kwak and T. Y. Seong, Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes, Appl. Phys. Lett.,2005,86,062103.
[6]K. Y. Ban, H. G. Hong, D. Y. Noh, J. I. Sohn, D. J. Kang and T. Y. Seong, Ir/Ag reflector for high-performance GaN-based near UV light emitting diodes, Mater. Sci.Eng.B,2006,133,26-29.
[7]J. Y. Kim, J. M. Lee and M. K. Kwon, Formation of low resistance and high reflectivity reflector on p-type GaN using Ni/Au/W/Ag ohmic contact, Solid state Lett.,2012,15, H198-H201.
[8]J. M. Lee, J. Yi, W. W. Lee, H. Y. Jeong, T. Jung, Y. Kim and W. II Park, ZnO nanorods-graphene hybrid structures for enhanced current spreading and light extraction in GaN-based light emitting diodes, Appl. Phys. Lett.,2012,100, 061107.
[9]C. L. Lin, P. H. Chen, C.-H. Chan, C. C. Lee, C.-Ch. Chen, J.-Y. Chang and C. Y. Liu, Light enhancement by the formation of an Al oxide honeycomb nanostructure on the n-GaN surface of thin-GaN light-emitting diodes, Appl. Phys. Lett.,2007, 90(24),242106.
[10]T. S. Kim, S.-M. Kim, Y. H. Jan and G. Y. Jung, Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography, Appl. Phys. Lett.,2007,91,171114.
[11]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2009,94(7), 071118.
[12]M.-K. Lee, C.-L. Ho and P.-C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photon. Technol. Lett., 2008,20(4),252-254.
[13]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett., 2010,22(16),1220-1222.
[14]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3), H120-H123.
[15]B. S. Kang, S. J. Pearton and F. Ren, Low temperature (<100℃) patterned growth of ZnO nanorod arrays on Si, Appl. Phys. Lett.,2007,90(8),083104.
[16]S. J. An, J. H. Chae, G. C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92(12), 121108.
[17]Z. Yin, X. Liu, Y. Wu, X. Hao, and X. Xu, Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays, Opt. Express,2012,20(2),1013-1021.
[1]X. Gao, X. Yan, X. Yao, L. Xu, K. Zhang, J. Zhang, B. Yang, and L. Jiang, The dry-tyle antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography, Adv. Mater.,2007,19(17),2213-2217.
[2]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[3]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[4]H.-W. Huang, C. C. Kao, J. T. Chu, H. C. Kuo, S. C. Wang and C. C. Yu, Improvement of InGaN-GaN Light-Emitting Diode Performance With a Nano-Roughened p-GaN Surface, IEEE Photon. Technol. Lett.,2005,17(5),983-985.
[5]M. Ma, J. Cho, E. F. Schubert, Y. Park, G. B. Kim and C. Sone, Strong light-extraction enhancement in GaInN light-emitting diodes patterned with TiO2 micro-pillars with tapered sidewalls, Appl. Phys. Lett.,2012,101,141105.
[6]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, 2009,17(23),21250-21256.
[7]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chen, Enhancement of light output intensity by integrating ZnO nanorod arrays on GaNbased LLO vertical LEDs, Electrochem. Solid-State Lett.,2008,11(4), H84-H87.
[8]D. Pudis, L. Suslik, J. Skriniarova, J. Kovac, I. Martincek, J. Kovac, Jr., S. Hascik, I. Kubicova, J. Novak and M. Vesely, Light extraction from a light emitting diode with photonic structure in the surface layer investigated by NSOM, Opt. Laser Technol.,2011,43(5),917-921.
[9]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett.,2010,22(16),1220-1222.
[10]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3), H120-H123.
[11]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2009,94(7), 071118.
[12]M.-K. Lee, C.-L. Ho and P.-C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photon. Technol. Lett., 2008,20(4),252-254.
[13]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett., 2010,22(16),1220-1222.
[14]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3),H120-H123.
[15]Y. M. Song, G. C. Park, S.J.Jang, J. H. Ha, J. S. Yu and and Y. T. Lee, Multifunctional light escaping architecture inspired by compound eye surface structures:From understanding to experimental demonstration, Opt. Express,2011, 19(S2),A157-A165.
[16]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, J. Appl. Phys.,2003,93,9383-9385.
[17]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[18]Y.-C. Chao, C.-Y. Chen, C.-A. Lin, Y.-A. Dai and J.-H. He, Antireflection effect of ZnO nanorod arrays, J. Mater. Chem.,2010,20(37),8134-8138.
[19]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90(20),203515.
[20]B. S. Kang, S. J. Pearton, and F. Ren, Low temperature (<100℃) patterned growth of ZnO nanorod arrays on Si, Appl. Phys. Lett.,2007,90(8),083104.
[21]X.-X. Fu, X.-N. Kang, B. Zhang, C. Xiong, X.-Z. Jiang, D.-S. Xu, W.-M. Du and G.-Y. Zhang, Light transmission from the large-area highly ordered epoxy conical pillar arrays and application to GaN-based light emitting diodes, J. Mater. Chem. 2011,21(26),9576-9581.
[22]X. L. Nguyen, T. N. N. Nguyen, V. T. Chau and M. C. Dang, The fabrication of GaN-based light emitting diodes (LEDs), Adv. Nat. Sci. Nanosci. Nanotechnol. 2010,1(2),025015.
[23]K. S. Kim, S. M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.
[24]A. N. Noemaun, F. W. Mont, G.-B. Lin, J. Cho, E. F. Schubert, G. B. Kim, C. Sone and J. K. Kim, Optically functional surface composed of patterned graded-refractive-index coatings to enhance light-extraction of GaInN light-emitting diodes, J. Appl. Phys.,2011,110(5),054510.
[25]M. K. Lee, C. L. Ho and P. C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photonics Technol. Lett., 2008,20(4),252-254.
[1]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[2]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[3]J.-T. Lian, J.-H. Ye, J.-Y. Liou, K.-C. Tsao, N.-C. Chenb and T.-Y. Lin, Improved light extraction efficiency on GaN LEDs by an In2O3 nano-cone, J. Mater. Chem. C,2013,1,6559-6564.
[4]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, 2009,17(23),21250-21256.
[5]S. J. Wang, P. R. Wang, D. M. Kuo, H. R. Kuo and Ji.-S. Kuo, Improved light output of GaN-based vertical light emitting diodes using SiO2 nanotube arrays and transparent metal oxide current conduction layer, Appl. Phys. Lett.,2011,99, 131111.
[6]P. Uthirakumar, J. H. Kang, B. D. Ryu, H. G. Kim, H. K. Kim and C.-H. Hong, Nanoscale ITO/ZnO layer texturing for high-efficiency InGaN/GaN light emitting diodes, Materials Science and Engineering B,2010,166,230-234.
[7]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90,203515.
[8]S. J. An, J. H. Chae, G.-C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92,121108.
[9]C. H. Chao, W. H. Lin, C. H. Chen, C. H. Changjean and C. F. Lin, Tunable Light extraction efficiency of GaN light emitting diodes by ZnO nanorod arrays. Semicond. Sci. Technol,2009,24,105017.
[10]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light Output Enhancement of GaN-based Light emitting Diodes Using ZnO nanorod Arrays Produced by Aqueous Solution Growth Technique, IEEE Photonics Technol. Lett., 2010,22(16),1220-1222.
[11]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chenb, Enhancement of Light Output Intensity by Integrating ZnO Nanorod Arrays on GaN-based LLO Vertical LEDs, Electrochem. Solid ST.,2008,11(4), H84-H87.
[12]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 Photonics Technol. Lett.,2008,20(4),252-254.
[13]Z. Yin, X. Liu, Y. Wu, X. Hao and X. Xu, Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays, Opt. Express,2012,20(2),1013-1021.
[14]X. Liu, W. Zhou, Z. Yin, X. Hao, Y. Wu and X. Xu, Growth of single-crystalline rutile TiO2 nanorod arrays on GaN light-emitting diodes with enhanced light extraction, J. Mater. Chem.,2012,22,3916-3921.
[15]S. Watanabe, N. Yamada, M. Nagashima, Y. Ueki, C. Sasaki, Y. Yamada, T. Taguchi, K. Tadatomo, H. Okagawa and H. Kudo, Internal quantum efficiency of highly-efficient Inx Gai-xN-based near-ultraviolet lightemitting diodes, Appl. Phys. Lett.,2003,83,490-4908.
[16]H. Wang, Z. Ji, S. Qu, Gang Wang, Y. Jiang, B. Liu, X. Xu and H. Mino, Influence of excitation power and temperature on photoluminescence in InGaN/GaN multiple quantum wells, Opt. Express,2012,20(4),3932-3940.
[17]K. S. Kim, S. M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.
[2]J. I. Pankove and M. J. Massoulie, Injection luminescence from gallium arsenide, Bull. Am. Phys. Soc.,1962,7,88.
[3]J. N. Holonyak and S. F. Bevacqua, Coherent (visible) light emission from Ga(ASI-xPx) junctions, Appl. Phys. Lett.,1962,1,82-83.
[4]S. Nakamura, M. Senoh and T. Mukai, P-GaN/N-InGaN/N-GaN double-hetero-structure blue-light-emitting diodes, Jpn. J. Appl. Phys.,1993,32, L8-L11.
[5]S. Nakamura and G. Fasol, The Blue Laser Diode:GaN based light emitters and lasers, Springer,1997,343.
[6]Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano and T. Mukai, White light emitting diodes with super-high luminous efficacy, J. Phys. D:Appl. Phys.,2010,43, 354002.
[7]http://www.led-professional.com/technology/light-generation/continues-to-push-the-boundaries-of-led-performance-by-breaking-300-lumens-per-watt-barrier
[8]毛兴武,张艳雯,周建军,祝大卫,新一代绿色光源LED及其应用技术,人民邮电出版社,2008,102.
[9]刘恩科,朱秉升,罗晋生,半导体物理学,国防工业出版社(第四版),2013,298-303.
[10]Y. Narukawa, M. Ichikawa, D. Sanga, M. Sano and T. Mukai, White light emitting diodes with super-high luminous efficacy, J. Phys. D:Appl. Phys.,2010,43, 354002.
[11]T. Nakamura, M. Satoh, Schottky barrier height of a new ohmic contact NiSi2 to n-type 6H-SiC, Solid-State Electron.,2002,46,2063-2067.
[12]申屠伟进,胡飞,韩彦军,薛松,罗毅,钱可元,GaN基发光二极管芯片光提取效率的研究,光电子·激光,2005,16,385-389.
[13]E. F. Schubert, Light-Emitting Diodes,2nd ed. (Cambridge University,2006).
[14]P.C. Tsaia, W.R. Chen, Y.K. Su and C.Y. Huang, Enhanced light output of InGaN LEDs with a roughened p-GaN surface using different TMGa flow rates in p-AlGaN layer, Appl. Surf. Sci.,2010,256(22),6694-6698.
[15]A. David, Surface-Roughened Light-Emitting Diodes:An Accurate Model, J. Disp. Technol.,2013,9(5),301-316.
[16]X. F. Zeng, S. C. Shei and S. J. Chang, SiO2 Nanopillars on Microscale Roughened Surface of GaN-Based Light-Emitting Diodes by SILAR-Based Method, J. Nanomater.,2013(2013),753230.
[17]P.-W. Huang and Y. Sermon Wu, Output Power of AlGaInP Light Emitting Diode Improved by Double Roughening AlGaInP Surfaces, Electrochem. Solid-State Lett.,2010,13(5), H163-H165.
[18]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, J. Appl. Phys.,2003,93,9383-9385.
[19]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[20]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.,2004,84,855-857.
[21]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[22]X. Gao, X. Yan, X. Yao, L. Xu, K. Zhang, J. Zhang, B. Yang and L. Jiang, The dry-tyle antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography, Adv. Mater.,2007,19(17),2213-2217.
[23]Y. M. Song, G. C. Park, S. J. Jang, J. H. Ha, J. S. Yu and and Y. T. Lee, Multifunctional light escaping architecture inspired by compound eye surface structures:From understanding to experimental demonstration, Opt. Express,2011, 19(S2),A157-A165.
[24]K. Tadatomo, H. Okagawa, Y Ohuchi, T. Tsunekawa, Y Imada, M. Kato and T. Taguchi, High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy, Jpn. J. Appl. Phys.2001,40, L583-L585.
[25]H. Gao, F. Yan, Y. Zhang, J. Li, Y. Zeng and G. Wang, Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro- and nanoscale, J. Appl. Phys.,2008,103,014314.
[26]J.-H.Lee, D.-Y. Lee, B.-W. Oh and J.-H. Lee, Comparison of InGaN-Based LEDs . Grown on Conventional Sapphire and Cone-Shape-Patterned Sapphire Substrate, IEEE T. Electron Dev.,57(1),157-163.
[27]C.-F. Lin, C.-Min Lin, K.-T. Chen, W.-. Huang, M.-S. Lin, J.-J. Dai, R.-H. Jiang, Y.-C. Huang and C.-Y. Chang, Blue light-emitting diodes with a roughened backside fabricated by wet etching, Appl. Phys. Lett.,2009,95,201102.
[28]H. G. Kim, H. K. Kim, H.Y. Kim, H. Jeong, S. Chandramohan, P. Uthirakumar, M. S. Jeong, J.-S. Lee, E.-K. Suh and C.-H. Hong, Enhanced air-cavity effect of periodically oriented embedded air protrusions for high-efficiency InGaN/GaN light-emitting diodes, Opt. Letters,2010,35(18),3012-3014.
[29]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-inverted-pyramid (AlxGai-x)0.5Ino.5P/GaP light-emitting diodes exhibiting>50% external quantum efficiency, Appl. Phys. Lett.,1999,75,2365-2367.
[30]X. H. Wang, P. T. Lai and H. W. Choi, The contribution of sidewall light extraction to efficiencies of polygonal lightemitting diodes shaped with laser micromachining, J. Appl. Phys.,2010,108,023110.
[31]S. S. Schad, M. Scherer, M. Seyboth and V. Schwegler, Extraction efficiency of GaN-based LEDs, phys. stat. sol. (a),2001,188,127-130.
[32]E. Yablonovitch, Inhibited spontaneous emission in solid-state physics and electronics, Phys. Rev. Lett.,1987,58,2059-2062.
[33]S. John, Strong localization of photons in certain disordered dielectric superlattices, Phys. Rev. Lett.,1987,58,2486-2489.
[34]D.H.Kim, C.O.Cho, Y.G.Roh, H. Jeon, Y. S. Park, J. Cho, J. S. Im, C. Sone, Y. Park, W. J. Choi, Q. H. Park, Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns, Appl. Phys. Lett.,2005,87,203508-203510.
[35]E. Matioli and C. Weisbuch, Impact of photonic crystals on LED light extraction efficiency:approaches and limits to vertical structure designs, J. Phys. D:Appl. Phys.,2010,43,354005.
[36]G. Shambat, B. Ellis, J. Petykiewicz, M, A. Mayer, T. Sarmiento, J. Harris, E. E. Haller and J.Vuckovic, Nanobeam photonic crystal cavity light-emitting diodes, Appl. Phys. Lett.2011,99,071105.
[37]H.-Y.Ryu and J.-I. Shim, Structural Parameter Dependence of Light Extraction Efficiency in Photonic Crystal InGaN Vertical Light-Emitting Diode Structures, IEEE J. Quantum Elect.,2010,46(5),714-720.
[38]X. X Fu, B. Zhang, X. N. Kang, J. Deng, C. Xiong, T. Dai, X. Jiang, TongJun Yu, Z. Chen and G. Y. Zhang, GaN-based light-emitting diodes with photonic crystals structures fabricated by porous anodic alumina template, Opt. Express,2011, 19(S5),A1104-A1108.
[39]S. J. Chang, C. F. Shen, W. S. Chen, C. T. Kuo, T. K. Ko, S. C. Shei, J. K. Sheu, Nitride-based light emitting diodes with indium tin oxide electrode patterned by imprint lithography, Appl. Phys. Lett.,2007,91,013504.
[40]S. Fan, P. Villeneuve and J. D. Joannopoulos, High extraction efficiency of spontaneous emission from slabs of photonic crystals, Phys. Rev. Lett.,1997,78, 3294-3297.
[41]M. Boroditsky, R. Vrijen, T. F. Krauss, R. Coccioli and R. Bhat, E. Yablonovitch, Spontaneous emission extraction and Purcell enhancement from thin-film 2-D photonic crystals, J. Lightwave Technol,1999,17,2096-2112.
[42]M. Boroditsky, T. F. Krauss and R. Coccioli, Light extraction from optically pumped light-emitting diode by thin-slab photonic crystals, Appl. Phys. Lett.,1999, 75,1036-1038.
[43]A. Fehrembach, S. Enoch and A. Sentenac, Highly directive light sources using two-dimensional photonic crystal slabs, Appl. Phys. Lett.,2001,79,4280-4282.
[44]A. David, T. Fujii, R. Sharma, K. McGroddy, S. Nakamura, S. P. Denbaars, E. L. Hu, C. Weisbuch and H. Benisty, Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution, Appl. Phys. Lett.,2006,88,081124-081126.
[45]J. J. Wierer, A. David and M. M. Megens, Ⅲ-nitride photonic-crystal light-emitting diodes with high extraction efficiency, Nat. photonics,2009,3,163-169.
[46]T. Doan, C. Chu, C. Chen, W. Liu, J. Chu, J. Yeh, H. Chen, F. Fan and C. Tran, Vertical GaN based Light Emitting Diodes on metal alloy substrate for solid state lighting application, Proc. of SPIE,2006,6134,61340G-1-6.
[47]M. A. Tsai, P. Yu, C. L. Chao, C. H. Chiu, H. C. Kuo, S. H. Lin,J. J. Huang, T.C. Lu and S. C. Wang, Efficiency enhancement and beam shaping of GaN-InGaN vertical-injection light-emitting diodes via high-aspect-ratio nanorod arrays, IEEE Photonics Technol. Lett.,2009,21,257-259.
[48]J. O. Song, J. S. Kwak and T. Y. Seong, Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes, Appl. Phys. Lett.,2005,86,062103.
[49]K. Y. Ban, H. G. Hong, D. Y. Noh, J. I. Sohn, D. J. Kang and T. Y. Seong, Ir/Ag reflector for high-performance GaN-based near UV light emitting diodes, Mater. Sci. Eng. B,2006,133,26-29.
[50]J. Y. Kim, J. M. Lee and M. K. Kwon, Formation of low resistance and high reflectivity reflector on p-type GaN using Ni/Au/W/Ag ohmic contact, Solid state Lett.,2012,15, H198-H201.
[51]J. S. Ha, S. W. Lee, H. J. Lee, H. J. Lee, S. H. Lee, H. Goto, T. Kato, K. Fujii, M. W. Cho and T. Yao, The fabrication of vertical light-emitting diodes using chemical lift-off process, IEEE Photonics Technol. Lett.,2008,20,175-177.
[52]W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romando and N. M. Johnson, InxGal-xN light emitting diodes on Si substrates fabricated by Pd-In metal bonding and laser lift-off, Appl. Phys. Lett.,2000,77, 2822-2824.
[53]J. J. Wierer, D. A. Steigerwald, M. R. Krames, J. J. O'Shea, M. J. Ludowise, G. Christenson, Y.-C. Shen, C. Lowery, P. S. Martin, S. Subramanya, W. Gotz, N. F. Gardner, R. S. Kern and S. A. Stockman, High-power AlGaInN flip-chip light-emitting diodes, Appl. Phys. Lett.,2001,78,3379-3381.
[54]S. J. Chang, W. S. Chen, S. C. Shei, C. F. Shen, T. K. Ko, J. M. Tsai, W. C. Lai, J. K. Sheu, A. J. Lin and S. C. Hung, GaN-Based power Flip-chip LEDs With Cu Submount, IEEE J. Sel. Top Quant.,2009,15(4),1287-1291.
[55]O. B. Shchekin, J. E. Epler, T. A. Trottier, T. Margalith, D. A. Steigerwald, M. O. Holcomb, P. S. Martin and M. R. Krames, High performance thin-film flip-chip InGaN-GaN light-emitting diodes, Appl. Phys. Lett.,2006,89(7),071109.
[56]J.-H. Lee, S.-M. Hwang, N.-S. Kim and J.-H. Lee, InGaN-Based High-Power Flip-Chip LEDs with Deep-Hole-Patterned Sapphire Substrate by Laser Direct Beam Drilling, IEEE Electr. Device L.,2010,31(7),698-700.
[57]S. H. Huang, R. H. Horng, K. S. Wen, Y. F. Lin, K.-W. Yen and D.-S. Wuu, Improved Light Extraction of Nitride-Based Flip-Chip Light-Emitting Diodes via Sapphire Shaping and Texturing, IEEE Photonics Technol. Lett.,2006,18(24), 2623-2625.
[58]R.-H.Horng, H.-L. Hu, M.-T. Chu, Y.-L. Tsai, Y.-J. Tsai, Ch.-P. Hsu and D.-S. Wuu, Performance of Flip-Chip Thin-Film GaN Light-Emitting Diodes With and without patterned Sapphire, IEEE Photonics Technol. Lett.,2010,22(8),550-552.
[59]J. M. Lee, J. Yi, W. W. Lee, H. Y. Jeong, T. Jung, Y. Kim and W. II Park, ZnO nanorods-graphene hybrid structures for enhanced current spreading and light extraction in GaN-based light emitting diodes, Appl. Phys. Lett.,2012,100, 061107.
[60]S.-Y. Jung and T.-Y. Seong, Improved light output power of GaN-based flip-chip light-emitting diode through SiO2 cones, Electro. Mater. Lett.,2012,8(6),549-552.
[61]C. L. Lin, P. H. Chen, Chia-Hua Chan, C. C. Lee, Chii-Chang Chen, Jeng-Yang Chang and C. Y. Liu, Light enhancement by the formation of an Al oxide honeycomb nanostructure on the n-GaN surface of thin-GaN light-emitting diodes, Appl. Phys. Lett.,2007,90(24),242106.
[62]T. S. Kim, S.-M. Kim, Y. H. Jan and G. Y. Jung, Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography, Appl. Phys. Lett.,2007,91,171114.
[63]J.-T. Lian, J.-H. Ye, J.-Y. Liou, K.-C. Tsao, N.-C. Chenb and T.-Y. Lin, Improved light extraction efficiency on GaN LEDs by an In2O3 nano-cone, J. Mater. Chem. C,2013,1,6559-6564.
[64]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, 2009,17(23),21250-21256.
[65]S. J. Wang, P. R. Wang, D. M. Kuo, H. R. Kuo and Ji.-S. Kuo, Improved light output of GaN-based vertical light emitting diodes using SiO2 nanotube arrays and transparent metal oxide current conduction layer, Appl. Phys. Lett.,2011,99, 131111.
[66]P. Uthirakumar, J. H. Kang, B. D. Ryu, H. G. Kim, H. K. Kim and C.-H. Hong, Nanoscale ITO/ZnO layer texturing for high-efficiency InGaN/GaN light emitting diodes, Mat. Sci. Eng. B,2010,166,230-234.
[67]Y.-C. Chao, C.-Y. Chen, C.-A. Lin, Y.-A. Dai and J.-H. He, Antireflection effect of ZnO nanorod arrays, J. Mater. Chem.,2010,20(37),8134-8138.
[68]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90,203515.
[69]S. J. An, J. H. Chae, G.-C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92,121108.
[70]K. S. Kim, S.-M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.
[71]H. Park, K.-J. Byeon, K.-Y. Yang, J.-Y. Cho and H. Lee, The fabrication of a patterned ZnO nanorod array for high brightness LEDs, Nanotechnology,2010, 21(35),355304.
[72]M.-S. Lin, C.-C. Chen, W.-C. Wang, C.-F. Lin and S.-Y. Chang, Fabrication of the selective-growth ZnO nanorods with a hole-array pattern on a p-type GaN:Mg layer through a chemical bath deposition process, Thin Solid Films,2010,518(24), 7398-7402.
[73]C. H. Chao, W. H. Lin, C. H. Chen, C. H. Changjean and C. F. Lin, Tunable Light extraction efficiency of GaN light emitting diodes by ZnO nanorod arrays. Semicond. Sci. Technol,2009,24,105017.
[74]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light Output Enhancement of GaN-based Light emitting Diodes Using ZnO nanorod Arrays Produced by Aqueous Solution Growth Technique, IEEE Photonics Technol. Lett., 2010,22(16),1220-1222.
[75]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chenb, Enhancement of Light Output Intensity by Integrating ZnO Nanorod Arrays on GaN-based LLO Vertical LEDs, Electrochem. Solid ST.,2008,11(4), H84-H87.
[76]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 Photonics Technol. Lett.,2008,20(4),252-254.
[77]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2008,94, 071118.
[78]X. Liu, W. Zhou, Z. Yin, X. Hao, Y. Wu and X. Xu, Growth of single-crystalline rutile TiO2 nanorod arrays on GaN light-emitting diodes with enhanced light extraction, J. Mater. Chem.,2012,22,3916-3921.
[79]M. Ma, J. Cho, E. F. Schubert, Y. Park, G. B. Kim and C. Sone, Strong light-extraction enhancement in GalnN light-emitting diodes patterned with TiO2 micro-pillars with tapered sidewalls, Appl. Phys. Lett.,2012,101,141105.
[80]K. M. Yoon, K. Y. Yang, K. J. Byeon and H. Lee, Enhancement of light extraction in GaN based LED structures using TiO2 nano-structures, Solid-State Electron., 2010,54,484-487.
[1]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, J. Appl. Phys.,2003,93,9383-9385.
[2]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[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.,2004,84,855-857.
[4]J. J. Wierer, A. David and M. M. Megens, Ⅲ-nitride photonic-crystal light-emitting diodes with high extraction efficiency, Nat. photonics,2009,3,163-169.
[5]J. O. Song, J. S. Kwak and T. Y. Seong, Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes, Appl. Phys. Lett.,2005,86,062103.
[6]K. Y. Ban, H. G. Hong, D. Y. Noh, J. I. Sohn, D. J. Kang and T. Y. Seong, Ir/Ag reflector for high-performance GaN-based near UV light emitting diodes, Mater. Sci.Eng.B,2006,133,26-29.
[7]J. Y. Kim, J. M. Lee and M. K. Kwon, Formation of low resistance and high reflectivity reflector on p-type GaN using Ni/Au/W/Ag ohmic contact, Solid state Lett.,2012,15, H198-H201.
[8]J. M. Lee, J. Yi, W. W. Lee, H. Y. Jeong, T. Jung, Y. Kim and W. II Park, ZnO nanorods-graphene hybrid structures for enhanced current spreading and light extraction in GaN-based light emitting diodes, Appl. Phys. Lett.,2012,100, 061107.
[9]C. L. Lin, P. H. Chen, C.-H. Chan, C. C. Lee, C.-Ch. Chen, J.-Y. Chang and C. Y. Liu, Light enhancement by the formation of an Al oxide honeycomb nanostructure on the n-GaN surface of thin-GaN light-emitting diodes, Appl. Phys. Lett.,2007, 90(24),242106.
[10]T. S. Kim, S.-M. Kim, Y. H. Jan and G. Y. Jung, Increase of light extraction from GaN based light emitting diodes incorporating patterned structure by colloidal lithography, Appl. Phys. Lett.,2007,91,171114.
[11]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2009,94(7), 071118.
[12]M.-K. Lee, C.-L. Ho and P.-C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photon. Technol. Lett., 2008,20(4),252-254.
[13]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett., 2010,22(16),1220-1222.
[14]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3), H120-H123.
[15]B. S. Kang, S. J. Pearton and F. Ren, Low temperature (<100℃) patterned growth of ZnO nanorod arrays on Si, Appl. Phys. Lett.,2007,90(8),083104.
[16]S. J. An, J. H. Chae, G. C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92(12), 121108.
[17]Z. Yin, X. Liu, Y. Wu, X. Hao, and X. Xu, Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays, Opt. Express,2012,20(2),1013-1021.
[1]X. Gao, X. Yan, X. Yao, L. Xu, K. Zhang, J. Zhang, B. Yang, and L. Jiang, The dry-tyle antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography, Adv. Mater.,2007,19(17),2213-2217.
[2]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[3]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[4]H.-W. Huang, C. C. Kao, J. T. Chu, H. C. Kuo, S. C. Wang and C. C. Yu, Improvement of InGaN-GaN Light-Emitting Diode Performance With a Nano-Roughened p-GaN Surface, IEEE Photon. Technol. Lett.,2005,17(5),983-985.
[5]M. Ma, J. Cho, E. F. Schubert, Y. Park, G. B. Kim and C. Sone, Strong light-extraction enhancement in GaInN light-emitting diodes patterned with TiO2 micro-pillars with tapered sidewalls, Appl. Phys. Lett.,2012,101,141105.
[6]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, 2009,17(23),21250-21256.
[7]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chen, Enhancement of light output intensity by integrating ZnO nanorod arrays on GaNbased LLO vertical LEDs, Electrochem. Solid-State Lett.,2008,11(4), H84-H87.
[8]D. Pudis, L. Suslik, J. Skriniarova, J. Kovac, I. Martincek, J. Kovac, Jr., S. Hascik, I. Kubicova, J. Novak and M. Vesely, Light extraction from a light emitting diode with photonic structure in the surface layer investigated by NSOM, Opt. Laser Technol.,2011,43(5),917-921.
[9]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett.,2010,22(16),1220-1222.
[10]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3), H120-H123.
[11]K.-K. Kim, S.-D. Lee, H. Kim, J.-C. Park, S.-N. Lee, Y. Park, S.-J. Park and S.-W. Kim, Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution, Appl. Phys. Lett.,2009,94(7), 071118.
[12]M.-K. Lee, C.-L. Ho and P.-C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photon. Technol. Lett., 2008,20(4),252-254.
[13]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light output enhancement of GaN-based lightemitting diodes using ZnO nanorod arrays produced by aqueous solution growth technique, IEEE Photon. Technol. Lett., 2010,22(16),1220-1222.
[14]J.-W. Kang, M.-S. Oh, Y.-S. Choi, C.-Y. Cho, T.-Y. Park, C. W. Tu and S.-J. Park, Improved light extraction of GaN-based green light-emitting diodes with an antireflection layer of ZnO nanorod arrays, Electrochem. Solid-State Lett.,2011, 14(3),H120-H123.
[15]Y. M. Song, G. C. Park, S.J.Jang, J. H. Ha, J. S. Yu and and Y. T. Lee, Multifunctional light escaping architecture inspired by compound eye surface structures:From understanding to experimental demonstration, Opt. Express,2011, 19(S2),A157-A165.
[16]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, J. Appl. Phys.,2003,93,9383-9385.
[17]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[18]Y.-C. Chao, C.-Y. Chen, C.-A. Lin, Y.-A. Dai and J.-H. He, Antireflection effect of ZnO nanorod arrays, J. Mater. Chem.,2010,20(37),8134-8138.
[19]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90(20),203515.
[20]B. S. Kang, S. J. Pearton, and F. Ren, Low temperature (<100℃) patterned growth of ZnO nanorod arrays on Si, Appl. Phys. Lett.,2007,90(8),083104.
[21]X.-X. Fu, X.-N. Kang, B. Zhang, C. Xiong, X.-Z. Jiang, D.-S. Xu, W.-M. Du and G.-Y. Zhang, Light transmission from the large-area highly ordered epoxy conical pillar arrays and application to GaN-based light emitting diodes, J. Mater. Chem. 2011,21(26),9576-9581.
[22]X. L. Nguyen, T. N. N. Nguyen, V. T. Chau and M. C. Dang, The fabrication of GaN-based light emitting diodes (LEDs), Adv. Nat. Sci. Nanosci. Nanotechnol. 2010,1(2),025015.
[23]K. S. Kim, S. M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.
[24]A. N. Noemaun, F. W. Mont, G.-B. Lin, J. Cho, E. F. Schubert, G. B. Kim, C. Sone and J. K. Kim, Optically functional surface composed of patterned graded-refractive-index coatings to enhance light-extraction of GaInN light-emitting diodes, J. Appl. Phys.,2011,110(5),054510.
[25]M. K. Lee, C. L. Ho and P. C. Chen, Light extraction efficiency enhancement of GaN blue LED by liquidphase-deposited ZnO rods, IEEE Photonics Technol. Lett., 2008,20(4),252-254.
[1]T. Wei, Q. Kong, J. Wang, J. Li, Y. Zeng, G. Wang, J. Li, Y. Liao and F. Yi, Improving light extraction of InGaN-based light emitting diodes with a roughened p-GaN surface using CsCl nano-islands, Opt. Express,2011,19(2),1065-1071.
[2]S.-I. Na, G.-Y. Ha, D.-S. Han, S.-S. Kim, J.-Y. Kim, J.-H. Lim, D.-J. Kim, K.-I. Min and S.-J. Park, Selective Wet Etching of p-GaN for Efficient GaN-Based Light-Emitting Diodes, IEEE Photonics Technol. Lett.,2006,18(14),1512-1514.
[3]J.-T. Lian, J.-H. Ye, J.-Y. Liou, K.-C. Tsao, N.-C. Chenb and T.-Y. Lin, Improved light extraction efficiency on GaN LEDs by an In2O3 nano-cone, J. Mater. Chem. C,2013,1,6559-6564.
[4]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, 2009,17(23),21250-21256.
[5]S. J. Wang, P. R. Wang, D. M. Kuo, H. R. Kuo and Ji.-S. Kuo, Improved light output of GaN-based vertical light emitting diodes using SiO2 nanotube arrays and transparent metal oxide current conduction layer, Appl. Phys. Lett.,2011,99, 131111.
[6]P. Uthirakumar, J. H. Kang, B. D. Ryu, H. G. Kim, H. K. Kim and C.-H. Hong, Nanoscale ITO/ZnO layer texturing for high-efficiency InGaN/GaN light emitting diodes, Materials Science and Engineering B,2010,166,230-234.
[7]J. Zhong, H. Chen, G. Saraf, Y. Lu, C. K. Choi, J. J. Song, D. M. Mackie and H. Shen, Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency, Appl. Phys. Lett.,2007,90,203515.
[8]S. J. An, J. H. Chae, G.-C. Yi and G. H. Park, Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays, Appl. Phys. Lett.,2008,92,121108.
[9]C. H. Chao, W. H. Lin, C. H. Chen, C. H. Changjean and C. F. Lin, Tunable Light extraction efficiency of GaN light emitting diodes by ZnO nanorod arrays. Semicond. Sci. Technol,2009,24,105017.
[10]S. Dalui, C.-C. Lin, H.-Y. Lee, C.-H. Chao and C.-T. Lee, Light Output Enhancement of GaN-based Light emitting Diodes Using ZnO nanorod Arrays Produced by Aqueous Solution Growth Technique, IEEE Photonics Technol. Lett., 2010,22(16),1220-1222.
[11]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao and S. Y. Chenb, Enhancement of Light Output Intensity by Integrating ZnO Nanorod Arrays on GaN-based LLO Vertical LEDs, Electrochem. Solid ST.,2008,11(4), H84-H87.
[12]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 Photonics Technol. Lett.,2008,20(4),252-254.
[13]Z. Yin, X. Liu, Y. Wu, X. Hao and X. Xu, Enhancement of light extraction in GaN-based light-emitting diodes using rough beveled ZnO nanocone arrays, Opt. Express,2012,20(2),1013-1021.
[14]X. Liu, W. Zhou, Z. Yin, X. Hao, Y. Wu and X. Xu, Growth of single-crystalline rutile TiO2 nanorod arrays on GaN light-emitting diodes with enhanced light extraction, J. Mater. Chem.,2012,22,3916-3921.
[15]S. Watanabe, N. Yamada, M. Nagashima, Y. Ueki, C. Sasaki, Y. Yamada, T. Taguchi, K. Tadatomo, H. Okagawa and H. Kudo, Internal quantum efficiency of highly-efficient Inx Gai-xN-based near-ultraviolet lightemitting diodes, Appl. Phys. Lett.,2003,83,490-4908.
[16]H. Wang, Z. Ji, S. Qu, Gang Wang, Y. Jiang, B. Liu, X. Xu and H. Mino, Influence of excitation power and temperature on photoluminescence in InGaN/GaN multiple quantum wells, Opt. Express,2012,20(4),3932-3940.
[17]K. S. Kim, S. M. Kim, H. Jeong, M. S. Jeong and G. Y. Jung, Enhancement of light extraction through the wave-guiding effect of ZnO sub-microrods in InGaN blue light-emitting diodes, Adv. Funct. Mater.,2010,20(7),1076-1082.