近年來, 由於氮化鎵材料具有較大的直接能隙, 漸漸的受到大家的重視, 因而, 衍生出許多相關產品, 例如 交通指示燈, 液晶顯示器的背光源, 用作照明的白光LED等等.
然而,氮化鎵發光二極體由於光取出效率的不足, 還是無法取代現有的日光燈系統. 這個問題主要來至於氮化鎵與空氣間折射係數相差很大所造成. 然而, 經由斯乃爾定律在室溫情況下,全反射角大約在23度左右. 這代表了光會有極大的部分在表面造成反射因而無法透射到空氣中.
在我實驗部分, 我想藉由在氮化鎵表面上做出粗糙化的結構, 來增加光子透射到空氣的機率, 因而改善光取出效率不理想的問題. 奈米級結構是一種可以增加表面粗化的結構可以用來改善光取出效率. 研究奈米級結構的目的, 是因為具有許多的應用, 除了發光二極體以外, 還常應用在場發射, 平面顯示器, 和藍寶石基板的圖形製作,等等.
在實驗部分我主要將重心擺在如何去得到奈米級結構. 採用了直接蝕刻跟間接蝕刻兩種方式. 後者是前者的改良. 藉由間接蝕刻方式得到的奈米級結構可以成功的控制它的大小與密度. 最後, 將所得到的氮化鎵奈米級結構應用在元件上面. 也成功的在光取出效率提升了80.5%的效果

Recently, III-nitride wide bandgap materials have aroused considerable interests due to various applications, such as traffic signals, back-side lighting in liquid crystal display, illumination lighting by white light emitting diodes (LEDs), and so on.
However, the light extraction efficiency of GaN LEDs is not ideal to take place of the fluorescent light. This problem is mainly for the differences of refractive indices between the GaN and air. Therefore, the critical angle for the interface is about 23o from Snell’s law under the room temperature. Therefore, it makes a great fraction of light unable to emit into the air.
In my experiment, I want to increase the GaN surface roughness in order to enhance the probability of photon passing through air and solve the light extraction efficiency problem. So the nano-structure which increases GaN surface roughness could be used to improve light extraction efficiency. The purposes of research nano-sturecute are many applications such as LEDs, field emitters, flat-panel displays, patterned sapphire substrate (PSS) and so on.
I mainly focus on how to obtain the GaN nano-structure in my experiment. The methods for GaN nano-structure are directly and indirectly etching methods. The latter technique is the improvement of the former one. And the nano-structure by indirectly method could be easily controlled the diameter and density for this structure. Finally, I fabricate the devices with GaN nano-structure. And it successfully enhances the light extraction efficiency 80.5%.

Chapter 1
[1] Isamu Akasaki, ”Nitride semiconductors-impact on the future world”, Journal of Crystal Growth 237-239, 905-911, 2002
[2] Harumasa YOSHIDA, Tatsuhiro URUSHIDO, Hideto MIYAKE and Kazumasa HIRAMATSU, “Formation of GaN Self-Organized Nanotips by Reactive Ion Etching”, Jpn. J. Appl. Phys. Vol. 40 , pp. L1301-L1304, 2001
[3] Kwangsue PARK, Jong-Soo LEE, Man-Young SUNG and Sangsig KIM,“Structural and Optical Properties of ZnO Nanowires Synthesized from Ball-Milled ZnO Powders” ,Jpn. J. Appl. Phys. Vol. 41, pp. 7317–7321 ,2002
[4] Quanli HU, Guoqing LI, Hiroshi SUZUKI1, Hiroshi ARAKI and Tetsuji NODA, “In Situ Growth of Isotopically Enriched 28Si Nanowires Using the Floating-Zone (FZ) Melting Method”, Jpn. J. Appl. Phys. Vol. 41, pp. L7–L 9, 2002
[5] Fengyan ZHANG, Robert BARROWCLIFF, Greg STECKER, Wei PAN, Deli WAN and Sheng-Teng HSU, “Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition”, Jpn. J. Appl. Phys. Vol. 41, pp. 7317–7321 ,2002
[6] Ching-Lien HSIAO, Li-Wei TU, Min CHEN, Zhi-Wei JIANG, Ni-Wan FAN, Yen-Jie TU and Kwang-Ru WANG, “Polycrystalline to Single-Crystalline InN Grown on Si(111) Substrates by Plasma-Assisted Molecular-Beam Epitaxy”, Japanese Journal of Applied Physics Vol. 44, No. 34, pp. L 1076–L 1079, 2005
[7] Chia-Feng Lin,a, Jing-Hui Zheng, Zhong-Jie Yang, and Jing-Jie Dai, “High-efficiency InGaN-based light-emitting diodes with nanoporous
GaN:Mg structure”, APPLIED PHYSICS LETTERS 88, 083121 ,2006

Chapter 2
[1] http://140.116.176.21/technique/20071112/SEM7000.pdf
[2] S.J. Pearton, J.C. Zolper, R.J. Shul, F. Ren, “GaN: Processing, defects, and devices”, J. Appl. Phys., 86, 1, 1999
[3] C. Youtsey,I. Adesida, G. Bulman, “Highly anisotripic photoenhanced wet etching of n-type GaN”, Appl. Phys. Lett., 71, 2151, 1997
[4] M.S. Minsky, M. White, and E.L. Hu, “Room-temperature photoenhanced wet etching of GaN”, Appl. Phys. Lett. 68, 1531, 1996
[5] P. Gillis, D.A. Choutov, P.A. Steiner, J. D. Piper, J. H. Crouch, P. M. Dove, and K. P. Martin, “Low energy electron-enhanced etching of Si(100) in hydrogen/helium direct-current plasma”, Appl. Phys. Lett. 66, 2475, 1995
[6] R.J. Shul, “In processing of Wide Bandgap Semiconductors”, edited by S.J. Pearton Noyes, Park Ridge, NJ, 1999
[7] Adesida, A. Mahajan, E. Andideh, M. Asif Khan, D.T. Olsen, and J.N. Kuznia, “Reactive ion etching of gallium nitride in silicon tetrachloride plasmas”, Appl. Phys, Lett. 63, 2777, 1993
[8] Adesida, A.T. Ping, C.Youtsey, T. Sow, M.Asif Khan, D.T. Olsen, J.N. Kuznia, “Characteristics of chemically assisted ion beam etching of gallium nitride”, Appl. Phys. Lett. 65, 889, 1994
[9] W. A. Harrison, “Electronic Structure and Properties of Solids”, Freeman, Sna Francisco, 1980
[10] S.J. Pearton, C. R. Abernathy, F. Ren, J. R. Lothian, P. W. Wisk, A. Katz, and C. Constantine, Semicond. Sci. Technol. 8, 310, 1993

Chapter 3
[1] Tong WU, Zhi-Biao HAO, Guang TANG and Yi LUO, “Dry Etching Characteristics of AlGaN/GaN Heterostructures Using Inductively Coupled H2/Cl2, Ar/Cl2 and BCl3/Cl2 Plasmas”, Jpn. J. Appl. Phys. Vol. 42, pp. L 257–L 259,2003
[2] Heiji WATANABE and Shinji MATSU, “GaAs Dry Etching Using Electron Beam Induced Surface Rection,” JJAP. VOL, 30, N0,11B
[3] Kiyoshi ASAKAWA, Takashi YOSHIKAWA, Shigeru KOHMOTO, Yoshihiro NAMBU and Yoshiimasa SUGIMOTO, “Chlorine-Base Dry Etching of III/V Compound Semiconductors for Optoelectronic Application”, Jpn, J, Appl. Phys. Vo 37 ,1998
[4] Akihiro MATSUTANI, Hideo OHTSUKI1 and Fumio KOYAMA, “In situ Observation of Etching Profile in Inductively Coupled Plasma Etchingof GaAs and InP using Long Distance Microscope”, Jpn. J. Appl. Phys. Vol. 42,pp. 426–427,2003
[5] Tohru NISHIBE and Shin-ya NUNOUE, “Dry Etching of InGaAsP/InP Structures by Reactive Ion Beam Etching Using Chlorine and Argon”, JAPANESE JOURNAL OF APPLIED PHYSICS, VOL. 29, NO. 12, pp. L2449-L2452, DECEMBER, 1990
[6] In Jae SONG, Seong Kuk LEE, Kyoyeol LEE, Sung Soo PARK and Jae Yong HAN, “Properties of Etched Ga- and N-Faces of Freestanding GaN Substrate Using Inductively Coupled Plasma-Reactive Ion Etching”, Jpn. J. Appl. Phys. Vol. 41 ,pp. L 317–L 319, 2002
[7] Chang-Chin YU, Chen-Fu CHU, Juen-Yen TSAI, Hung Wen HUANG, Tao-Hung HSUEH, Chia-Feng LIN and Shing-Chung WANG, “Gallium Nitride Nanorods Fabricated by Inductively Coupled Plasma Reactive Ion Etching”, Jpn. J. Appl. Phys. Vol. 41 ,pp. L 910–L 912, 2002

Chapter 4
[1] Liann-Be CHANG, Su-Sir LIU and Ming-Jer JENG, “Etching Selectivity and Surface Profile of GaN in the Ni, SiO2 and Photoresist Masks”, Jpn. J. Appl. Phys. Vol.(40) , pp. 1242-1243, 2001
[2]Chang-Chin YU, Chen-Fu CHU, Juen-Yen, TSAI, Hung Wen Hung HSUEH, “Gallium Nitride nanorods Fabricated by Inductively Coupled Plasma Reactive Ion Etching”,Jpn. J. Appl. Phys. Vol. 41,pp. L910-L912, 2002
[3]Hung-Wen Huanga, Chih-Chiang Kaoa, Tao-Hung Hsueha, Chang-Chin Yub, Chia-Feng Linc, Jung-Tang Chua, Hao-Chung Kuoa, Shing-Chung Wang, “Fabrication of GaN-based nanorod light emitting diodes using self-assemble nickel nano-mask and inductively coupled plasma reactive ion etching” ,Materials Science and Engineering B 113,125–129, 2004

Chapter 5
[1] Chul Huh, Kug-Seung Lee, and Seong-Ju Park, “Enhanced performances of InGaN-based light-emitting diode by a micro-roughened p-GaN surface usin metal clusters”, Proc. Of SPIE Vol. 4776
[2] Wei Chih Peng and Yew Chung Semon Wu, “Improved luminance intensity of InGaN-GaN light-emitting diode by roughening both the p-GaN surface and the undoped-GaN surface“, APPLED PHYSICS LETTERS 89, 041116, 2006
[3] S. Ruvimov, Z. L. Weber, J. Washburn, K. J. Duxstad, E. E. Haller, Z.F. Fan, S.N. Moharmmad, W. Kim, A. E. Botchkarev, and H. Morkoc, “Microstructure of Ti/ Al and Ti/ Al/Ni/Au Ohmic contacts for n-GaN”, Appl. Phys. Lett. 69, 1556, 1996
[4] Hung-Wen Huang, J T Chu, “Enhanced light output of an InGaN/GaN light emitting diode with a nano-roughened p-GaN surface”, INSTITUTE OF PHYSICS PUBLISHING, Nanotechnology 16 , 1844-1848, 2005