臺灣博碩士論文加值系統

具高品質磊晶層之磷化鋁鎵銦(AlGaInP)發光二極體(Light Emitting Diode, LED)內部量子效率可高達99%，但是在外部量子效率方面卻仍有所侷限，主要原因是由於半導體與外部介質的折射率(n)差異太大。舉例而言:光從磷化鎵(GaP)材料(n = 3.5)行進至空氣(n = 1)中時，由斯乃爾定律(Snell''s law)可得知，只有光在小於臨界角17°內的光可以被射出，這樣結果表示絕大多數的光將會被介面全反射。本實驗證實藉由使用代號GaP-1蝕刻液對AlGaInP LED進行表面結構化處理，可以改善上述光萃取效率低落的缺點，研究中我們利用電激發光光譜儀來量測光電特性，並且使用光學顯微鏡與掃描式電子顯微鏡分析發光二極體外觀形貌。在比較結構化表面處理LED 與標準的LED 之後，我們發現到具紋理結構化表面的LED，在注入電流20毫安培下，其發光強度增加了約25%，而且發光主波長的變異性仍能控制在1%以下，電壓特性方面亦並無明顯的衰減。推測光輸出功率有明顯提昇的原因，應與在p-GaP窗口層表面形成紋理結構有關，因為表面形成紋理結構將有助於往外的光更能夠脫離LED散射到空氣中，進而增加了光的取出效率。藉由以上正面的實驗結果可知，要得到高亮度、高效率的AlGaInP LED將可以利用具紋理結構化表面的製程技術來實現。

Internal quantum efficiency of a high-quality AlGaInP LED epilayer can approach 99%, but external quantum efficiency is limited due to large refraction index difference between the semiconductor and the outside medium. An example in which light crosses an interface from GaP materials with a refractive index of 3.5 to air with a refractive index of 1 results in a small escape cone with an escape cone angle of 17° for emitted light, representing most total internal reflection light. We have demonstrated improved light extraction from textured AlGaInP light-emitting diodes (LEDs) by using wet etching with a GaP-1 etching solution. The LED properties were characterized by electroluminescence and surface morphology was analyzed by optical microscope and scanning electron microscope. When comparing the textured and the conventional LED, we found that the surface-textured LED exhibits a 25% power intensity improvement at 20 mA. The dominant wavelength variation was under 1% and the voltage variation did not degrade. The output power improvement in the surface-textured LED can be attributed to the formation of surface texture structure at the top GaP surface. This textured surface enabled some light, outside of the escape cone (~17°), to escape through the semiconductor to air interface resulting in additional light extraction. These positive results indicate that high performance AlGaInP LEDs can be achieved by employing a textured surface structure.

目錄
中文摘要I
英文摘要III
致謝V
目錄VI
圖表索引VIII
第一章 序論
1-1 研究背景1
1-2 研究動機3
第二章 基本原理
2-1 發光二極體工作原理5
2-2 直接能隙與間接能隙6
2-3 化合物半導體發光材料7
2-4 LED發光效率與光損耗機制8
2-5 菲涅爾損失(Fresnel Loss)9
2-6 全反射臨界角損失(Critical Angle Loss)10
2-7 LED表面結構化處理重要性11
第三章 實驗量測系統
3-1 掃瞄式電子顯微鏡(Scanning Electron Microscopy, SEM)簡介20
3-1.1 SEM原理21
3-1.2 SEM試片的製備22
3-1.3 SEM應用範圍23
3-2原子力顯微鏡(Atomic Force Microscope, AFM)簡介23
3-2.1 AFM的量測架構及成像原理24
3-2.2 AFM試片的製備26
3-2.3 AFM應用範圍26
第四章 實驗樣品結構與製程步驟
4-1實驗樣品結構與基本製程簡介32
4-1.1 實驗樣品結構32
4-1.2 晶片清洗(Wafer Cleaning)32
4-1.3 黃光微影(Photo-Lithography)技術定義電極圖形區域33
4-1.4 蒸鍍p-type歐姆接觸金屬34
4-1.5 蒸鍍n-type歐姆接觸金屬34
4-2 具表面紋理結構化LED元件製程35
4-2.1 GaP-1蝕刻液成份組成35
4-2.2 對元件進行表面紋理結構化處理36
4-2.3 元件間之隔絕(Isolation)36
第五章 結果與討論
5-1 OM與SEM之表面形態分析39
5-2 AFM之表面結構化程度分析40
5-3 LED工作電流-順向電壓之元件特性分析40
5-4 LED輸出光強度-工作電流之元件特性分析41
5-5 LED發光波長-電流之元件特性分析42
5-6 LED輻射場型圖之元件特性分析42
5-7 LED壽命測試43
第六章 總結與未來工作
6-1 總結58
6-2 未來工作59
參考文獻60
圖表索引
圖 1-1 LED應用面示意圖4
圖 2-1 同質接面在(a)未加偏壓(b)外加順向偏壓能帶圖12
圖 2-2 異質接面在(a)未加偏壓(b)外加順向偏壓能帶圖13
圖 2-3 (a)直接能隙與(b)間接能隙之能帶圖14
圖 2-4 室溫下，發光波長對應III-V化合物半導體材料能隙與晶格常數關係圖15
圖 2-5 室溫下，化合物半導體發光材料與波長關係圖16
圖 2-6 Fresnel損耗示意圖17
圖 2-7 臨界角損耗示意圖18
圖 2-8 光子在半導體中散射之示意圖19
圖 3-1 掃描式電子顯微鏡系統示意圖27
圖 3-2 電子束撞擊試片所產生之訊號之範圍與空間分佈情況28
圖 3-3 原子力顯微鏡的系統示意圖29
圖 3-4 兩原子間的距離與相對位能的關係圖30
圖 3-5 原子力顯微鏡操作模式示意圖31
圖 4-1 (a)標準LED結構(b)紋理結構化LED結構38
圖 5-1 浸泡GaP-1蝕刻液時間長短與SEM表面型態(a)未蝕刻前、(b)1分鐘、(c)3分鐘、(d)5分鐘、(e)14分鐘44,45,46
圖 5-2 具紋理結構化表面磷化鋁鎵銦發光二極體SEM之側壁觀察47
圖 5-3 圖 5-2之p-GaP窗口層的放大影像48
圖 5-4 蝕刻時間5分鐘P型金屬與p-GaP窗口層底切之情形(a)側視圖、(b)俯視圖、(c)底切較嚴重的部份49,50
圖 5-5 蝕刻液時間長短之AFM表面型態情形(a)未蝕刻前、(b)5分鐘、(c)14分鐘51,52
圖 5-6 LED電流-電壓之特性關係圖53
圖 5-7 LED光輸出強度-電流之特性關係圖54
圖 5-8 LED之發光波長-工作電流特性關係圖55
圖 5-9 LED之輻射場型圖56
圖 5-10 LED室溫20 mA之壽命測試曲線57

中文部份:
王耀興 “高效率藍光二極體之研究” 國立台灣大學光電工程研究所碩士論文 (2001)
林建宏 “磊晶技術在發光二極體表面改變粗糙狀況對發光效率的影響” 國立成功大學電機所在職專班碩士論文(2007)
英文部分:
A. David, H. Benisty and C. Weisbuch, “Optimization of light-diffracting photonic crystals for high extraction efficiency LEDs,” IEEE J. Displ. Technol., vol. 3, no. 2, pp. 133-148, 2007.
B. Puers and W. Sansen, “Compensation structures for convex corner micromachining in Silicon,” Sensors and Actuators A, vol. 23, no. 1, pp.1036–1041, 1990.
C. C. Yang, C. F. Lin, R. H. Jiang, H. C. Liu, C. M. Lin, C. Y. Chang, D. S. Wuu, H. C. Kuo and S. C. Wang, “Wet mesa etching process in InGaN-based light emitting diodes,” Electrochem. and Solid-State Lett., vol. 11, no. 7, pp. H169–H172, 2008.
C. E. Lee, H. C. Kuo, Y. C. Lee, M. R. Tsai, T. C. Lu, S. C. Wang and C. T. Kuo, “Luminance enhancement of flip-chip light emitting diodes by geometric sapphire shaping structure,” IEEE Photon. Technol. Lett., vol. 20, no. 3, pp. 184–186, 2008.
C. F. Shen, S. J. Chang, W. S. Chen, T. K. Ko, C. T. Kuo and S. C. Shei, “Nitride-based high-power flip-chip LED with double-side patterned sapphire substrate,” IEEE Photon. Technol. Lett., vol. 19, no. 10, pp. 780–782, 2007.
C. M. Sheu, J. K. Tsai, W. C. Lai, Y. P. Hsu, P. T. Wang, C. T. Kuo, C. W. Kuo, S. J. Chang and Y. K. Su, “Enhanced output power in GaN-based LEDs with naturally textured surface grown by MOCVD,” IEEE Electron Device Lett., vol. 26, no. 7, pp. 464–466, 2005.
E. Learner, “Solid-state illumination is on the horizon, but challenges remain,” Laser Focus World, November 2002.
G. B. Stringfellow and M.G. Craford, “High brightness lighting emitting diodes,” Academic Press, Boston, 1997.
H. Sugawara, M. Ishikawa and G. Hatakoshi, “High-efficiency InGaAlP/GaAs visible light-emitting diodes,” Appl. Phys. Lett., vol. 58, no. 10, pp. 1010–1012, Mar. 1991.
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., vol. 17, no. 5, pp. 983–985, 2005.
J. M. Titchmarsh, G.. R. Booker, W. Harding and D. R. Wight, “Carrier recombination at dislocations in epitaxial gallium phosphide layers,” J. Mater. Sci., vol. 12, no. 2, pp. 341–346, 1977.
J. Q. Xi, M. Ojha, W. Cho, C. Wetzel, T. Gessmann, E. F. Schubert, J. L. Plawsky and W. N. Gill, “Internal omni-directional reflector using a low refractive index material for light-emitting diodes,” Lasers and Electro-Optics, vol. 1, no. 22, pp. 144–146, 2005.
L. M. Landsberger, S. Naseh, M. Kahrizi and M. Paranjape, “On hillocks generated during anisotropic etching of Si in TMAH,” J. Micro Electro Mechanical Systems, vol. 5, no. 2, pp. 106-116, 1996.
L. R. Plauger, “Controlled chemical etching of GaP,” J. Electrochem. Soc., vol. 121, no. 3, pp. 455–457, 1974.
M. Boroditsky, T. F. Krauss, R. Coccioli, R. Vrijen, R. Bhat and E. Yablonovitch. “Light extraction from optically pumped light-emitting diode by thin-slab photonic crystals,” Appl. Phys. Lett., vol. 75, no. 8, pp. 1036-1038, 1999.
M. Kendall and M. Scholand, “Energy savings potential of solid state lighting in general lighting applications,” US Department of Energy, Washington, DC, 2001.
M. M. Abu-Zeid, “Corner undercutting in anisotropically etched isolation contours,” J. Electrochem. Soc., vol. 131, no 9, pp 2138–2142, 1984.
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, M. G. Craford, T. S. Tan, C. P. Kocot, M. Hueschen, J. Posselt, B. Loh, G. Sasser and D. Collins, “High power truncated inverted pyramid (AlxGa1-x)0.5In0.5P/GaP light emitting diodes exhibiting >50% external quantum efficiency,” Appl. Phys. Lett., vol. 75, no. 16, pp. 2365–2367, 1999.
O. Shmatov and Z. S. Li, “Truncated inverted pyramid light emitting diode geometry optimization using ray tracing technique,” IEEE Proceedings: Optoelectronics, vol. 150, no. 3, pp. 273–277, 2003.
O. Tabata, “PH-controlled TMAH etchants for silicon micromachining,” Sensors and Actuators A, vol. 53, no. 1, pp. 335–339, 1996.
P. C. Liu and Y. C. S. Wu, “Bonding line-patterned In0.5Ga0.5P layer on GaP substrate for the successive growth of high-brightness LED structures, ”Electrochemical and Solid-State Lett., vol. 8, no. 2, pp. G31–G34, 2005.
R. L. Meek and N. E. Schumaker, “Anodic dissolution and selective etching of gallium phosphide,” J. Electrochem. Soc., vol. 119, no. 9, pp. 1148–1152, 1972.
R. M. Fletcher, C. P. Kuo, T. D. Osentowski, K. H. Huang, M. C. Craford and V. M. Robbins, “The growth and properties of high performance AlGaInP emitters using a lattice mismatched GaP window layer,” J. Electron. Mater., vol. 20, no. 12, pp. 1125–1130, 1991.
R. Williams, “Modern GaAs processing methods,” 2nd. Boston. London Artech House, pp. 95-114, 1990.
S. H. Huang, R. H. Horng, S. C. Hsu, T. Y. Chen and D. S. Wuu, “Surface texturing for wafer-bonded vertical-typed GaN/mirror/Si light emitting diodes,” Jpn. J. Appl. Phys., vol. 44, no. 5, pp. 3028–3031, 2005.
S. H. Su, C. C. Hou, M. Yokoyama and S. M. Chen, “InGaN/GaN light emitting diodes with Ni/Au mesh p-contacts,” Solid-State Electronics, vol. 49, no. 12, pp. 1905–1908, 2005.
S. J. Chang, C. F. Shen, M. H. Hsieh, C. T. Kuo, T. K. Ko, W. S. Chen and S. C. Shei, “Nitride-based LEDs with a hybrid Al mirror +TiO2/SiO2 DBR backside reflector,” J. Lightwave Technol., vol. 26, no. 7, pp. 3131–3136, 2009.
S. J. Leem, Y. C. Shin, K. C. Kim, E. H. Kim, Y. M. Sung, S. M. Hwang and T. G. Kim, “The effect of the low-mole InGaN structure and InGaN/GaN strained layer superlattices on optical performance of multiple quantum well active layers,” J. Cryst. Growth, vol. 311, no. 1, pp. 103–106, 2008.
S. K. Kim, H. K. Cho, K. K. Park, J. Jang, J. S. Lee, K. W. Park, Y. Park, J. Y. Kim and Y. H. Lee, “Angle-tuned, evanescently-decoupled reflector for high-efficiency red light-emitting diode,” Optics Express, vol. 16, no. 9, pp. 6026–6032, 2008.
S. Nakamura, M. Senoh and T. Mukai, “P-GaN/N-InGaN/N-GaN double heterostructure blue-light emitting diodes,” Jpn. J. Appl. Phys., vol. 32, vol. 1, pp. L8–L11, 1992.
S. S. Tan, M. L. Reed, H. Han and R. Boudreau, “Mechanisms of etch hillock formation,” J. Micro Electro Mechanical Systems, vol. 5, no. 1, pp. 66-72, 1996.
T. Drennen, R. Haitz and J. Tsao, “A market diffusion and energy impact model for solid-state lighting,” 21st Annual North American Conference of the US Association of Energy Economics and International Association for Energy Economics, Philadelphia, 2000. T. Gessmann and E. F. Schubert, “High efficiency AlGaInP light emitting diodes for solid-state lighting applications,” J. Appl. Phys., vol. 95, no. 5, pp. 2203–2216, 2004.
W. K. Choi, J. T. L. Luo, P. Tan, C. M. Chua, T. H. and Y. Bai, “Characterization of pyramid formation arising from the TMAH etching of silicon,” Sensors and Actuators A, vol. 71, no. 3, pp. 238-243, 1998.
Y. Backlund and L. Rosengren, “New shapes in（100）Si using KOH and EDP etches,” J. Micromech. Microeng., vol. 2, no. 2, pp. 75–79, 1992.
Y. K. Bhatnagar and A. Nathan, “On pyramidal protrusions in anisotropic etching of <100> silicon,” Sensors and Actuators A, vol. 36, no. 3, pp. 233-240, 1993.
Y. W. Cheng, H. H. Chen, M. Y. Ke, C. P. Chen and J. J. Huang, “Effect of selective ion-implanted p-GaN on the junction temperature of GaN-based light emitting diodes,” Optics Communications, vol. 282, no. 5, pp. 835–838, 2009.