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研究生: 彭榆鈞
Peng Yu-Jun
論文名稱: 增進LED光萃取效率之GaN膜粗化蝕刻技術開發
Development on improving extraction efficiency of GaN LEDs by surface roughing technique of wet etching
指導教授: 楊啓榮
Yang, Chii-Rong
學位類別: 碩士
Master
系所名稱: 機電工程學系
Department of Mechatronic Engineering
論文出版年: 2007
畢業學年度: 95
語文別: 中文
論文頁數: 204
中文關鍵詞: 氮化鎵表面粗化雷射掀離法氮面
英文關鍵詞: GaN, surface roughing, laser lift-off, n-face
論文種類: 學術論文
相關次數: 點閱:250下載:0
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  • 氮化鎵發光二極體(GaN LED)光萃取效率不佳,是其一直存在的問題,而對於提升光萃取效率,通常最簡易也最為有效的技術,莫過於粗化技術。GaN中之光子,因GaN的高折射係數( n=2.5 ),依施乃耳定律,臨界角僅有23.6°,光子也只能在此臨界角所形成的光逃脫角錐內,才能順利的穿過邊界,達到空氣之中。藉由粗化技術,可破壞臨界角的限制,光子因此不易產生全反射且易於脫離原本介質,進而提升其光萃取效率。GaN主要有兩種極性方向-鎵面與氮面,在鎵面上非常穩定且不易蝕刻,故可藉由雷射掀離法將薄膜掀離,並轉換到另一基材上,經由此技術後,薄膜較不穩定的氮面便會翻轉向上,藉此便可輕易的藉由溼式蝕刻技術,製作出大面積的六角錐柱。
    本研究主要目的,是利用溼式蝕刻技術,與添加劑YR、YC、YP、T-X與Y-A的使用,藉此改變氮面上的表面能,進而改變錐柱的形態與控制錐柱的角度。本研究也已成功的藉由YR添加劑的使用,在YR與50 wt.%.的KOH溶液為10 ml : 1 liter比例上,將原本六角錐柱,改變成圓錐之形態。角度方面,也可以藉各種添加劑比例上的配合,將角錐控制在65-120°的範圍內。本研究也將此新式的蝕刻技術與一般的粗化技術相比較,在350 mA的驅動下,105°的圓錐形態,比一般的六角錐粗化,其光輸出功率高出了7 %左右,此原因即為此種新式的蝕刻技術所製造之圓錐,可使側向的光子路徑皆為法線方向,因此提升其光萃取效率。以上的結果顯示出,在表面形態上,本研究所提出之蝕刻技術,以優於一般傳統的六角錐柱之蝕刻。

    Light extraction efficiency is always a problem for GaN LED. And surface roughing is simple and useful technology for raising light extraction efficiency. Because of GaN with high refraction coefficient (n=2.5), by Snell’s law, it can create a critical angle of 23.6° and just allow photons escaping from original medium in this escape cone made by critical angle. But we can overcome this rule to raise light extraction efficiency by surface roughing technology. There are two polarization direction for GaN, those are: Ga-face and n-face. Ga-face is too stable to etch for creating rough surface, but n-face is easy to make it. So we can transform sapphire to another substrate and take GaN film up-side down by laser lift off (LLO). By LLO, we can etch the surface easily to fabricate hexagonal cones of large area on n-face.
    In this study, we will change surface energy of n-face to change shape and control angle of hexagonal cones by additives, and those additives are YR, YC, YP, T-X and Y-A. By YR, we can change hexagonal cones to cones. And we also can control angle of cone by mixed additives. In this study, we have ability to control angle what the range is 65°~120° by this novel etching technology. Comparison between conventional LED with hexagonal cones of 70° and our LED with cones of 105°, power efficiency of ours is higher than conventional LED with hexagonal cones about 7%
    .

    總 目 錄 摘要 Ⅲ 總目錄 Ⅴ 圖目錄 IX 表目錄 XX 第一章 緒論 1 1.1 前言 1 1.2氮化鎵LED發展歷史 2 1.2.1 GaN材料的發展歷史 2 1.2.2 提升GaN發光效率之發展歷史 3 1.2.3 內部量子效率的提升 3 1.2.4 外部量子效率的提升 4 1.3 GaN未來之展望 6 1.4 論文動機 7 第二章 氮化鎵發光二極體之相關原理 16 2.1 發光二極體發光效率 16 2.1.1量子效率 16 2.1.2功率轉換效率 16 2.2 光損失機制 17 2.2.1材料吸收以及電流分布不均之損失 17 2.2.2 Fresnel損失 19 2.2.3臨界角損失 19 2.3 GaN晶格與濕式蝕刻特性 21 2.3.1 Ga-face與N-face 22 2.3.2 Ga-face的濕式蝕刻 22 2.3.3 N-face的濕式蝕刻 23 第三章 文獻回顧 33 3.1 前言 33 3.2 萃取效率之提升 33 3.3.1藉由幾何形狀提升萃取效率 34 3.3.2覆晶式LED (flip-chip LED, FC-LED) 39 3.3.3表面組織結構與粗化技術 41 第四章 實驗設計與規劃 89 4.1 實驗規劃 89 4.2 n-face溼式蝕刻之粗化製程規劃 90 4.3 實驗與量測設備 92 4.4 角度測量原則與傾斜所產生的誤差之修正 93 4.4.1角度測量原則 93 4.4.2因傾斜角所展生的誤差之修正 93 4.5 錐柱尺寸與密度計算原則 93 4.5.1錐柱尺寸之計算 94 4.5.2錐柱密度計算 95 4.6預期之目標 95 第五章 實驗結果與討論 113 5.1 主添加劑YR效果之探討 113 89 5.1.1 添加YR之實驗結果 113 5.1.2 YR添加量與形態之關係 115 5.1.3 YR添加量、垂直與側向蝕刻速率以及角度之關係 115 5.1.4 角度與錐柱形態之關係 115 5.1.5 YR添加量、形態與角錐密度之關係 117 5.2 YR與副添加劑之實驗 118 5.2.1 YR與YC之實驗結果 117 5.2.2 YR與YP之實驗結果 119 5.2.3 YR與T-X 100之實驗結果 120 5.2.4 小結 120 5.3 YR與輔助添加劑Y-A之實驗 120 5.3.1 添加Y-A蝕刻與純粹KOH蝕刻之比較 120 5.3.2 主添加劑YR與Y-A之相關實驗 121 5.3.3 副添加劑YC與Y-A之相關實驗 121 5.3.4 副添加劑YP與Y-A之相關實驗 122 5.3.5 副添加劑T-X與Y-A之相關實驗 122 5.3.6 主、副添加劑與Y-A並用之相關實驗 123 5.3.6.1 YR、YC與Y-A並用之相關實驗 123 5.3.6.2 YR、YP與Y-A並用之相關實驗 123 5.3.6.3 YR、T-X與Y-A並用之相關實驗 124 5.3.7 小結 124 5.4 主添加劑與兩種以上之副添加劑之實驗 125 5.4.1 YP + YC + YR 125 5.4.2 YP + YC + T-X + YR 125 5.4.3 YC + T-X + YR 126 5.4.4 YP + T-X + YR 126 5.5 均勻度之探討 126 5.5.1 兩種不均勻之情況 127 5.5.1.1 因蝕刻速率的不同所導致的不均勻 127 5.5.1.2 因反應沉積物之產生所導致的不均勻 127 5.5.2 因YR所產生不均勻狀況之討論 128 5.5.3 因YP所產生不均勻狀況之討論 129 5.6 提升均勻度的方法之討論 129 5.6.1 改善分子團聚集之方法討論 130 5.6.1.1 磁石攪拌輔助 130 5.6.1.2 機械式攪拌輔助 130 5.6.1.3 超音波震盪輔助 130 5.6.1.4 提高溫度輔助 131 5.6.1.5 藉由改變蝕刻溶液之濃度 131 5.5.1.6 藉由均勻溫度的分布之輔助 132 5.6.2 改善反應沉積物所導致不均勻狀況之方法討論 132 5.7 光強度之實際測試 133 5.8 圓錐形態與六角錐形態之比較 135 第六章 結論 194 參考文獻 196

    1. T. Mukai, M. Yamda and S. Nakamura,”Characteristics of InGaN-Based UV/Blue/Green/Amber/Red Light-Emitting Diodes", Japanese Journal of Applied Physics, Vol. 38, NO. 7A, pp. 3976–3981(1999).
    2. H. Amano, M. Kito, K. Hiramatsu, K. Hiramatsu and I. Akasaki,”P-type conduction in Mg-doped GaN treated with low-energy electron beam irradiation (LEEBI)", Japanese Journal of Applied Physics, Vol. 28, NO. 12, pp. 2112–2114(1989).
    3. S. Nakamura, T. Mukai, M. Senoh, and N. Naruhito, Japanese Journal of Applied Physics”Thermal annealing effects on p-type Mg-doped GaN films”, Vol. 31, NO. 31, pp. 139–142(1992)
    4. S. Nakamura, T. Mukai and M. Senoh,”Candela-class high-brightness InGaN/AIGaN double-heterostructure blue-light-emitting”, Applied Physics Letters, Vol. 64, NO. 13, pp. 1687–1689(1994)
    5. S. Nakamura, M. Senoh, N. Iwasa, and S. I. Nagahama" High-power InGaN single-quantum-well-structure blue and violet light-emitting diodes” ,Applied Physics Letters , Vol. 67, NO. 13, pp. 1868–1870(1995)
    6. S. Nakamura, T. Mukai and M. Senoh,” High-power AlGaInN flip-chip light-emitting diodes”, Applied Physics Letters, Vol. 64, NO. 13, pp. 1687–1689(1994)
    7. 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. Go¨ tz, N. F. Gardner, R. S. Kern, and S. A. Stockman,” High-power AlGaInN flip-chip light-emitting diodes”, Applied Physics Letters , Vol. 78, NO. 22, pp. 3379–3381(2001).
    8. 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”, Journal of Applied Physics, Vol. 93, NO. 11, pp. 9383–9385(2003).
    9. M. Yamada, T. Mitani, Y. Narukawa, S Shioji, I. Niki, S. Sonobe, K. Deguchi, M. Sano and T. Mukai” InGaN-Based near-ultraviolet and blue-light-emitting diodes with high external quantum efficiency using a patterned sapphire substrate and a mesh electrode", Japanese Journal of Applied Physics, Vol. 41, NO. 12B, pp. 1431–1433(2002).
    10. Y. Gao, T. Fuji, R. Sharma, K. Fujito, S. P. Denbaars, S. Nakamura and E. L. HU,” Roughening hexagonal surface morphology on laser lift-off (LLO) n-face GaN with simple photo-enhanced chemical wet etching", Journal of Applied Physics, Vol. 43, NO. 5A, pp. 637–639(2004).
    11. E. F. Schubert,”Light-emitting diodes”, 2003
    12. T. Kozawa, T. Kachi, T. Ohwaki, and Y. Taga,”Dislocation etch pits in GaN epitaxial layers grown on sapphire substrates”, Journal of the Electrochemical Society, Vol. 143, NO. 1, pp. 17–19(1996).
    13. C. Youtseya and I. Adesida,”Highly anisotropic photoenhanced wet etching of n-type GaN”, Applied Physics Letters , Vol. 71, NO. 15, pp. 2151–2153(1997).
    14. T. Rotter, D. Mistele, J. Stemmer, F. Fedler, J. Aderhold, and J. Graul,” Photoinduced oxide film formation on n-type GaN surfaces using alkaline solutions", Applied Physics Letters , Vol. 76, NO. 26, pp. 3923–3925(2000).
    15. W. S. Wong, T. Sands, and N. W. Cheung” Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off”, Applied Physics Letters , Vol. 75, No. 10, pp. 1360-1362 (1999).
    16. I. Fonseca,”The Wulff Theorem”, Mathematical and Physical Sciences, Vol. 432, No. 1884, pp. 125-145(1991).
    17. W. N. Carr and G. E. Pittman,”One-watt GaAs p-n junction infrared source”, Applied Physics Letters , Vol. 3, No. 10, pp. 1962-1964 (1963).
    18. A. R. Franklin and R. E. Newman,”Shaped electroluminescent GaAs diodes”, Journal of Applied Physics , Vol. 35, No. 4, pp. 1153-11155 (1964).
    19. M. R. Krames, M. O.Holcomb, G. E. Hofler, C. C. 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 (AlxGa1-x)00.5In00.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency", Applied Physics Letters , Vol. 75, No. 16, pp. 2365-2367 (1999).
    20. W. Schmid, M. Scherer, C. Karnutsch, A. Plößl, W. Wegleiter, S.-S. Schad, B. Neubert, and K. Streubel,”High-efficiency red and infrared light-Emitting diodes using radial outcoupling taper” ,IEEE Journal on Selected Topics in Quantum Electronics, Vol. 8, No. 2, pp. 256-263 (2002).
    21. T. K. Yoo, S. H. Hahm and Y. S. Kwon,”Surface emitting AlGaAs/GaAs DH LED with buried window cylindrical lens”, Japanese Journal of Applied Physics, Vol. 27, NO. 12, pp. 2357–2360(1988).
    22. E. H. Puk, J. Ho Kim, T. K. Yoo and Y. S. Kwon,”Bell shaped light emitting diode(BS-LED) with 45° corner reflector, deep side-wall and microlens”, SPIE, Vol. 4641, pp. 19-30 (2002).
    23. J. Baur, B. Hahn, M. Fehrer, D. Eisert, W. Stein, A. Plossl, F. Kuhn, H. Zull, M. Winter, and V. Harle,”InGaN on SiC LEDs for high flux and high current applications”, Physica status solidi, Vol. 194, NO. 2, pp. 399-402 (2002).
    24. S. S. Schad, M. Scherer, M. Seyboth and V. Schwegler,”Extraction Efficiency of GaN-Based LEDs”, Physica status solidi, Vol. 188, NO. 1, pp. 127-130 (2001).
    25. S. J. Lee and S. W. Song,”Efficiency improvement in 1ightemitting diodes based on geometrically deformed chips", SPIE, Vol. 3621, NO. 1, pp. 237-248 (1999).
    26. C. C. Kao, H. C. Kuo, H. W. Huang, J. T. Chu, Y. C. Peng, Y. L. Hsieh, C. Y. Luo, and S. C. Wang,”Light–output enhancement in a nitride-based light-emitting diode with 22o undercut sidewalls”, IEEE Photonics Technology Letters, Vol. 17, NO. 1, pp. 19-21 (2005)
    27. M. Koike, N. Shibata, H. Kato and Y. Takahashi,”Development of High Efficiency GaN-Based Multiquantum-Well Light-Emitting Diodes and Their Applications", IEEE Journal on Selected Topics in Quantum Electronics, Vol. 8, No. 2, pp. 271-277 (2002).
    28. J. J. Wierer, J. C. Bhat, C.-H. Chen, G. Christenson, L. W. Cook, M. G. Craford, N. F. Gardner, W. Götz, R. S. Kern, R. Khare, A. Kim, M. R. Krames, M. J. Ludowise, R. Mann, P. S. Martin, M. Misra, J. O'Shea, Y. C. Shen, F. M. Steranka, S. A. Stockman, S. Subramanya, S. L. Rudaz, D. A. Steigerwald and J. Yu, "High-power A1InGaN light-emitting diodes", SPIE, Vol. 4278, pp. 127-132 (200).
    29. A.Y. Kim, W. Gotz, D.A. Steigerwald, J. J. Wierer, N. F. Gardner, J. Sun, S.A. Stockman, P.S. Martin, M.R. Krames, R.S. Kern, and F.M. Steranka, "Performance of high-power AlInGaN light emitting diodes", Physica status solidi, Vol. 188, NO. 1, pp. 15-21 (2001).
    30. I. Schnitzer and E. Yablonovitch, "30% external quantum efficiency from surface textured, thin-film light-emitting diodes", Applied Physics Letters , Vol. 63, No. 16, pp. 2174-2176 (1993).
    31. R. Windisch, C. Rooman, B. Dutta, A. Knobloch, G. Borghs, G. H. Döhler, and P. Heremans, "Light-extraction mechanisms in high-efficiency surface-textured light-emitting diodes", IEEE, Vol. 8, No. 2, pp. 248-255 (2002).
    32. W. K. Wang, S. Y. Huang, S. H. Huang, K. S. Wen, and D. S. Wuu, "Fabrication and efficiency improvement of micropillar InGaN/Cu light-emitting diodes with vertical electrodes", Applied Physics Letters , Vol. 88, pp. 181113-1~181113-3(2006).
    33. C. H. Kuo, C. M. Chen, and C. W. Kuo, "Improvement of near-ultraviolet nitride-based light emitting diodes with mesh indium tin oxide contact layers", Applied Physics Letters , Vol. 89, pp. 201104-1~201104-3(2006).
    34. E. J. Kang, C. Huh, S. H. Lee, J. J. Jung, S. J. Lee, and S. J. Parke, "Improvement in light-output power of InGaN/GaN LED by formation of nanosize cavities on p-GaN surface", Electrochemical and Solid-State Letters, Vol. 8, No. 12, pp. 327-329(2005).
    35. M. S. Minsky, M. White, and E. L. Hu, "Room-temperature photoenhanced wet etching of GaN", Applied Physics Letters , Vol. 68, No. 11, pp. 1531-1533(1996).
    36. C. Youtsey, L. T. Romano and I. Adesida, "Gallium nitride whiskers formed by selective photoenhanced wet etching of dislocations", Applied Physics Letters , Vol. 73, No. 6, pp. 797-799(1998).
    37. H. M. Ng, N. G. Weimann, and A. Chowdhury, "GaN nanotip pyramids formed by anisotropic etching", Journal of Applied Physics, Vol. 94, No. 1, pp. 650–653(2003)
    38. H. M. Ng, N. G. Weimann, and A. Chowdhury, "Patterning GaN Microstructures by Polarity-Selective Chemical Etching", Japan Journal of Applied Physics, Vol. 42, No. 12A, pp. 1405–1407(2003)
    39. V. Härle, B. Hahn, J. Baur, M.Fehrer, A. Weimar, S. Kaiser, D. Eisert, F. Eberhard, A. Plössl and S. Bader, "Advanced Technologies for high efficiency GaInN LEDs for solid state lighting", SPIE, Vol. 5187, pp. 34–40(2004).
    40. B. S. Tan and S. Yuan, "Performance enhancement of InGaN light-emitting diodes by laser lift-off and transfer from sapphire to copper substrate", Applied Physics Letters, Vol. 84, No. 15, pp. 2757-2759(2004).
    41. S. J. Lee, "Design rules for high-brightness light emitting diodes grown GaAs substrate", Japan Journal of Applied Physics, Vol. 37, No. 2, pp. 509–516(1998).
    42. C. S. Chang, S. J. Chang, Y. K. Su, C. T. Lee, Y. C. Lin, W. C. Lai, S. C. Shei, J. C. Ke, and H. M. Lo, "Nitride-based LEDs with textured side walls", IEEE Photonics Technology Letters, Vol. 16, NO. 3, pp. 750-752 (2004).
    43. Y. J. Lee, H. C. Kuo, S. C. Wang, T. C. Hsu, M. H. Hsieh, M. J. Jou, and B. J. Lee, "Increasing the extraction efficiency of AlGaInP LEDs via n-side surface roughening", IEEE Photonics Technology Letters, Vol. 17, NO. 11, pp. 2289-2291 (2005).
    44. W. C. Peng and Y. C. S. Wu, "Enhanced light output in double Roughened GaN light-emitting diodes via various texturing treatments of undoped-GaN layer", Japan Journal of Applied Physics, Vol. 45, No. 10A, pp.7709–7712 (2006).
    45. W. C. Peng and Y. C. S. Wu, " Improved luminance intensity of InGaN–GaN light-emitting diode by roughening both the p-GaN surface and the undoped-GaN surface", Applied Physics Letters, Vol. 89, No. 041116, pp. 1-3(2006).
    46. T. Fujii, A. David, Y. Gao, M. Iza, S. P. DenBaars, E. L. Hu, C. Weisbuch, and S. Nakamura "Cone-shaped surface GaN-based light-emitting diodes" , Physica status solidi, Vol. 2, NO. 7, pp. 2836-2840 (2005).

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