本論文研究使用雷射雙光束干涉微影法製作次微米光柵結構於發光二極體(Light Emitting Diodes，LEDs)表面，目的為改善光萃取效率，並且對於LEDs的光型調制、光場分布與發光極化率作探討，文中使用的模擬分析法為有限時域差分法(Finite Difference Time Domain，FDTD)，模擬結果顯示次微米光柵結構週期為1?m且深度為250nm時可以提升出光強度達88%。
在實驗製程上，我們利用干涉曝光微影技術將干涉條紋轉印至發光二極體元件上的光阻層，再利用感應耦合電漿蝕刻系統 (Inductively coupled plasma，ICP)蝕刻轉印至發光元件表面。因此我們可得到不同尺寸的次微米光柵，藉以探討結構參數變異對於光萃取效率以及光型調制的影響。
經由模擬運算及角度解析光激發螢光(Angle-Resolved photoluminescence，ARPL) 量測結果的比較，我們發現次微米光柵可以破壞氮化鎵結構內的光波導模態(waveguide mode)，使結構內部的光經由次微米光柵萃取出來，當次微米光柵週期小於1?m且蝕刻深度為200nm時，其光萃取效率能夠有效的提高，其中效率最高為週期=900nm的結構參數，其出光增強率可達到74%。
由ARPL量測光型分佈可以得到未做結構之LED的0o至正負30o其出光強度會有15%的衰減；但是當週期為900nm時，其0o至正負30o的出光強度只有10%的衰減；週期為800nm和1?m時則有13%的衰減，這個結果可證明次微米光柵結構有助於提升發光二極體的正面出光均勻度。
而固定0o與30o的收光角度所量測的極化率結果，發現具光柵結構之LEDs其極化率在0o及30o時分別為14.3%及25.4%；然而未做結構之LED的極化率在0o及30o時分別為1.8%及1.7% 。因此具光柵結構之LEDs其極化現象更為明顯。

In this thesis, we use the two beam interference lithograph to fabricate sub-micron grating structures on the surface of GaN-based light-emitting diodes (LEDs) for improving the light extraction efficiency. We simulate the light extraction efficiency and the field distribution of the flat and the sub-micron grating LEDs by the finite-difference time-domain method. There is an 88% improvement on light extraction efficiency of the LED with the grating period of 1?m. We fabricate the sample and use the angle-resolved photoluminescence (ARPL) and angle-resolved electroluminescence (AREL) to measure the field distribution and light extraction efficiency. The output intensity of the LEDs with sub-micron gratings is significantly enhanced by 74%, compared with that without structure. According to the ARPL results, the LED with sub-micron grating structures will improve the uniformity of field distribution and the polarization ratio of extracted light.

[1] 陳隆建 (2006). ''發光二極體之原理與製程'' 全華科技圖書股份有限公司.
[2] Yoshitaka Koyama "Ray-Tracing simulation in LCD development," Sharp Technical Journal 80, 51-55 (2001)
[3] Optical Research Associates "選擇正確的照明設計軟體," www.opticalres.com, (2008)
[4] Dong-Ho Kim, et al. "Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns," Appl. Phys. Lett. 87, 203508 (2005)
[5] Sun-Kyung Kim, et al. "Efficient GaN slab vertical light-emitting diode covered with a patterned high-index layer," Appl. Phys. Lett. 92, 241118 (2008)
[6] H. Kim, et al. "Light-extraction enhancement of vertical-injection GaN-based light-emitting diodes fabricated with highly integrated surface trxtures," Opt. Lett. 33, 1273 (2008)
[7] C. H. Chan, et al. "Patterning perioidical motif on substeates using monolayer of microspheres: Application in GaN light-emitting diodes," Jpn. J. Appl. Phys. 48, 020212 (2009)
[8] C. H. Chiu, et al. "Nano-processing techniques applied in GaN-based light-emitting devices with self assembly Ni nano-masks," J. Lihgtwave Technol. 26, 1445 (2008)
[9] C. H. Kuo, et al. "Nitride-based near-ultraviolet light emitting diodes with meshed p-GaN," Appl. Phys. Lett. 90, 142115 (2007)
[10] C. H. Kuo, et al. "Photo-enhanced chemical wet etching of GaN," Mat. Sci. Eng. B-Solid State Mater. Adv. Technol. 96, 43 (2002)
[11] H. W. Hunag, et al. "Enhanced light output of an InGaN/GaN light emitting diode with a nano-roughened p-GaN surface," Nanotechnology 16, 1844 (2005)
[12] H. W. Hunag, et al. "Enhanced light output from a nitride-based power chip of green light-emitting diodes with nano-rough surface using nanoimprint lithography," Nanotechnology 19, 185301 (2008)
[13] R. H. Horng, et al. "Light extraction enhancement of InGaN light-emitting diode by roughening both undoped micropillar-structure GaN and p-GaN as well as empolying an omnidirectional reflector," Appl. Phys. Lett. 93, 021125 (2008)
[14] R. Windish, et al. "Impact of texture-enhnaced transmission of high-efficiency surface-textured light-emitting diodes," Appl. Phys. Lett. 79, 2315 (2001)
[15] A. A. Erchak, et al. "Enhnaced couplig to vertical radiation using a two-dimensional photonic crystal in a semiconductor lgiht-emitting diode," Appl. Phys. Lett. 78, 563 (2001)
[16] A. David, et al. "Photonic bands in two-dimensionally patterned multimode GaN waveguides for light extraction," Appl. Phys. Lett. 87, 101107 (2005)
[17] A. L. Fehrembach, et al. "Highly directive light source using two-dimensional photonic crystal slabs," Appl. Phys. Lett. 79, 4280 (2001)
[18] C. F. Lai, et al. "Anisotropy of light extraction from GaN two-dimensional photonic crystals," Opt. Express 16, 7285 (2008)
[19] H. K. Cho, et al. "Light extraction enhancement from nano-imprinted photonic crystal GaN-based blue light-emitting diodes," Opt. Express 14, 8654 (2006)
[20] H. K. Cho, et al. "Laser liftoff GaN thin-film photonic crystal GaN-based light-emitting diodes," IEEE Photon. Technol. Lett. 20, 2096 (2008)
[21] H. Matsubara, et al. "GaN photonic-crystal surface-emitting laser at blue-violet wavelengths," Science 319, 445 (2008)
[22] H. Ichikawa, et al. "Efficiency enhancement in a light-emitting diode with a two-dimensional surface grating photonic crystal," Appl. Phys. Lett. 84, 457 (2004)
[23] K. Bergenek, et al. "Enhanced light extraction efficiency from AlGaInP thin-film light-emitting diodes with photonic crystals," Appl. Phys. Lett. 93, 041105 (2008)
[24] K. McGroddy, et al. "Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes," Appl. Phys. Lett. 93, 103502 (2008)
[25] M. R. Krames, et al. "High-power truncated-inverted-pyramid (Al0.5Ga1-x)0.5In0.5P/GaP light-emitting diodes exhibiting>50% external quantum efficiency," Appl. Phys. Lett. 75, 2365 (1999)
[26] A. Köck , et al. "Strongly directional emission from AlGaAs/GaAs light-emitting diodes," Appl. Phys. Lett. 57, 2327 (1990)
[27] A. Neogi, et al. "Enhancement of spontaneous recombination rate in a quantum well by resonant surface plasmon coupling," Phys. Rev. B 66 66, 153305 (2002)
[28] Dong-Ming Yeh, et al. "Surface plasmon coupling effect in an InGaN/GaN single-quantum-well light-emitting diode," Appl. Phys. Lett. 91, 171103 (2007)
[29] I. Gontijo, et al. "Coupling of InGaN quantum-well photoluminescence to silver surface plasmons," Phys. Rev. B 60 60, 11564 (1999)
[30] J. Vuckovic, et al. "Surface plasmon enhanced light-emitting diode," Quantum Electronics, IEEE Journal of 36, 1131-1144 (2000)
[31] 楊侍蒲 (2009). 次微米光柵結構改善發光二極體光萃取效率及其光型調制之研究. 光電科學研究所碩士論文, 中央大學.
[32] E. F. Schubert (2003). ''Light Emitting Diodes'' Cambridge, England, Dambridge University Press.
[33] A. David, et al. "Optimization of light-diffracting photonic-crystals for high extraction efficiency LEDs," J. Disp. Technol. 3, 133 (2007)