相對於以藍寶石基板為主已商業化之橫向結構氮化鎵系列發光二極體，本論文旨在研發具垂直結構與金屬基板之高效率氮化鎵系列發光二極體(VM-LEDs)。我們提出一種結合電鍍(Electroplating)及區塊雷射剝離(Patterned laser lift-off)之技術置換藍寶石基板，以解決絕緣的藍寶石基板因散熱不佳、橫向傳導所帶來電流叢聚效應(Current crowding effect)以及兩電極位在同一表面造成較小發光面積等問題，進而提升光輸出功率以及發光效率。此外，我們亦使用乾蝕刻(Dry-etching)-電感耦合電漿(ICP)與化學蝕刻(Chemical etching)-氫氧化鉀(KOH)溶液同時進行n-GaN表面處理並進行垂直元件製作，由實驗證實，使用最佳化的粗化條件：60oC、6莫耳(mol)氫氧化鉀溶液浸泡90秒進行表面粗化之VM-LED，於20 mA操作下亮度增加超過兩倍，而順向壓降(Vf)與傳統差異不大。
於大面積VM-LED研製方面，本研究提出一種Indium Zinc Oxide (IZO)透明導電層作為n-GaN之電流擴展層，期使VM-LED具其有更好的電流擴散及更高的發光效率。於製程方面，於ICP乾蝕刻去除u-GaN後的n-GaN表面濃度僅約為1018cm-3，對大面積、高功率GaN-based LED將衍生嚴重之電流叢聚效應，故須配合電極設計進行改善。此處我們提出一種利用濺鍍方式沉積一擁有高濃度(將近1021 cm-3)之透明導電層(IZO layer)並結合金屬基板製作大面積VM-LED。為取得IZO層與n-GaN磊晶層間之良好歐姆接觸，其介面間係以一鈦(Ti=10 Å)中間層作為因應。IZO透明導電層之沉積係利用射頻濺鍍系統以90 W射頻功率，通入流量20 sccm的純氬氣，反應腔壓力則維持在5×10-3 torr。實驗結果顯示，採用15分鐘之濺鍍，所獲得IZO薄膜厚度約300 nm，電阻率為3×10-4 W-cm，於藍光波長區間(465 - 475 nm)其穿透率為85%左右，對元件之光輸出功率之改善上呈現最佳之表現，而元件之順向偏壓與其串聯電阻亦優於傳統橫向式元件者。
於40 mil-LED之實驗結果亦顯示，覆蓋IZO(300nm)透明導電薄膜之元件，於350 mA工作電流條件下光輸出功率，可比傳統元件增加達97%，且串聯電阻均較傳統平面式元件降低60%以上，順向偏壓降低0.2 V，其Power Efficiency提升超過兩倍。此一結果可看出，採用適當厚度之IZO透明導電薄膜不論是在節省能源或是延長元件壽命上皆有極大助益。
此外，為因應金屬基板切割時之剪應力及金屬噴濺所造成元件漏電問題，我們亦開發出一種選擇性電鍍(Selective electroplating)並結合區塊雷射剝離技術之製程技術，提供一種可避開金屬基板切割及降低成本免切割VM-LED (Dicing-free VM-LED)有效方法。再者，為了提升區塊鎳上保留雷射剝離後磊晶之完整性及減少元件側壁漏電的可能性，我們沉積SiO2作為保護並適度安排使元件剝離尺寸小於區塊鎳尺寸，以大幅提升剝離後磊晶完整之良率。經實驗結果證實，此方式所製得VM-LED元件其發光效率之提升量與整面電鍍金屬基板VM-LED者旗鼓相當。

In this study, use of electroplating and pattern laser lift-off techniques to replace sapphire substrate by an electroplated nickel (Ni) metal substrate and the fabrication of vertical-structured metallic-substrate GaN-based light-emitting diodes (LEDs) (abbreviated as VM-LEDs) were presented. As compared to conventional GaN-based LEDs with sapphire substrate (abbreviated as regular LEDs), the increase in light output power (Lop) and luminous efficiency of VM-LEDs is attributed to the benefits of good heat-sink, shorter conduction path, less current crowding effect, and larger effective area. Furthermore, additional surface treatment of n-GaN, employing dry-etching by inductive coupled plasma (ICP) and wet-etching by KOH solution, to obtain high efficient VM-LEDs was made. As was evident from the experimental results, under an injection current of 20 mA, the lop of VM-LEDs via surface roughening with the condition of 6-mol KOH solution at 60C for 90s is about two times than regular ones, while maintaining low forward voltage drop as compared to regular LEDs.
To tackle the current crowding effect in the fabrication of large area LEDs causing by not enough doping concentration of the top n-GaN (<51018 cm-3), a transparent and low-resistant indium-zinc oxide (IZO) film was proposed to serve as a current spreading layer (CSL) for VM-LEDs. In addition, nickel electroplating and patterned laser lift-off (LLO) techniques were also employed for the transfer of sapphire substrate to realize a vertical structure device. Based on experimental results, IZO CSL atop n-side up VM-LEDs does offer benefits of superior current spreading ability, larger extraction efficiency, and lower forward voltage drop as expected. As compared to regular LEDs without IZO CSL, the use of an IZO CSL with an optimum thickness of around 300 nm leads to an increase in light output power (Lop) by 97.1 (67.8)% and a decrease in forward voltage drop by 4.9 (15.5)% under an injection current of 350 (800) mA.
To overcome dicing difficulty encountered by the use of Ni electroplating substrate and improve device yield, a novel process using a patterned Ni electroplating, instead of blanket electroplating, was proposed and demonstrated. In conjunction with a sidewall passivation with SiO2 and keeping the size of epilayer smaller than that of Ni islands, considerable improvements in yield and device performance were achieved. As compared to conventional regular LEDs, an increase in light output power about 174% at 350 mA with a significant decrease in forward voltage drop from 3.5 V to 3.17 V were obtained.

Chapter 1:
[1] E. F. Schubert, “Light-Emitting Diodes”, Cambridge University, 2003.
[2] S. Nakamura and G. Fasol, “The Blue Laser Diode”, Springer-Verlag, Heidelberg, 1997.
[3] S. Strite and H. Morkoc, “GaN, ALN, and InN: A review”, J. Vac. Sci. Technol. B vol. 10, pp. 1237-1266, July 1992.
[4] C. Humphreys, “Compound Semiconductor”, p. 14, May 2003.
[5] H. W. Huang, J. T. Chu, C. C. Kao, T. H. Hseuh, T. C. Lu, H. C. Kuo, S. C. Wang, and C. C. Yu, “Enhanced light output of an InGaN/GaN light emitting diode with a nano-roughened p-GaN surface”, Nanotechnology, vol. 16, pp. 1844–1848, 2005.
[6] C. H. Kuo, S. J. Chang, Y. K. Su, R. W. Chuang, C. S. Chang, L. W. Wu, W. C. Lai, J. F. Chen, J. K. Sheu, H. M. Lo, and J. M. Tsai, “Nitride-based near-ultraviolet LEDs with an ITO transparent contact”, Materials Science and Engineering B, vol. 106, pp. 69–72, 2004.
[7] R. A. Logan, H. G. White, and W. Wiegmann, “Efficient green electroluminescence in nitrogen-doped GaP p-n junctions”, Appl. Phys. Lett., vol. 13, pp. 139-141, Aug. 1968.
[8] C. Huh, J. M. Lee, D. J. Kim, and S. J. Park, “Improvement in light-output efficiency of InGaN/GaN multiple-quantum well light-emitting diodes by current blocking layer”, J. Appl. Phys., vol. 92, pp. 2248-2250, Sep. 1986.
[9] 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, 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, pp. 2365-2368, Oct. 1999.
[10] J. Y. Tsao, “Light Emitting Diodes (LEDs) for General Illumination”, Sandia National Laboratories, Optoelectronics Industry Development Association (OIDA), Nov. 2002.
[11] M. K. Kelly, O. Ambacher, B. Dahlheimer, G. Groos, R. Dimitrov, H. Angerer, and M. Stutzmann, “Optical patterning of GaN films”, Appl. Phys. Lett. vol. 69, pp. 1749-1751, Sep. 1996.
[12] 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. vol. 84, pp. 855-857, Apr. 2004.
[13] M. G. Craford, presented at the Nanoscience and Solid State Lighting Department of Energy Nanosummit,Washington, D.C, 2004.
[14] J. J. Wierer, D. A. Steigerwa, 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. vol. 78, pp. 3379-3381, May 2001.

Chapter 2:
[1] S. Yoshida, S. Misawa, and S. Gonda, “Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN-coated sapphire substrates”, Appl. Phys. Lett., vol. 42, pp. 427-429, Mar. 1983.
[2] H. Amano, N. Sawaki, I. Akasaki, and Y. Touoda, ”Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer”, Appl. Phys. Lett., vol. 48, pp. 353-355, Feb. 1986.
[3] H. Amano, M. Iwaya, T. Kashima, M. Katsuragawa, I. Akasaki, J. Han, S. Hearne, J.A. Floro, E. Chason, and J. Figiel, ”Stress and Defect Control in GaN Using Low Temperature Interlayers”, Jpn. J. Appl. Phys., vol. 37, pp. L1540-L1542, 1998.
[4] B. Beaumont, Ph. Vennegures, and P. Gibart, “Epitaxial Lateral Overgrowth of GaN”, Phys. Stat. Sol. (b), vol. 227, pp. 1-43, Sep. 2001.
[5] R. F. Davis, T. Gehrke, K. J. Linthicum, P. Rajagopal, A. M. Roskowski, T. Zheleva, E. A. Preble, C. A. Zorman, M. Mehregany, U. Schwarz, J. Schuck, and R. Grober, ”Review of Pendeo-Epitaxial Growth and Characterization of Thin Films of GaN and AlGaN Alloys on 6H-SiC(0001) and Si(111) Substrates, “MRS Internet Journal of Nitride Semiconductor Research”, vol. 6, pp. 1-16, Nov. 2001.
[6] C. I. H. Ashby, C. C. Mitchell, J. Han, N. A. Missert, P. P. Provencio, D. M. Follstaedt, G. M. Peake, and L. Griego, “Low-dislocation-density GaN from a single growth on a textured substrate”, Appl. Phys. Lett., vol. 77, pp. 3233-3235, Nov. 2000.
[7] H. Morkoc, S. Strite, G. B. Gao, M. E. Lin, B. Sverdlov, and M. Burns, “Large-band-gap SiC, III-V nitride, and II-VI ZnSe-based semiconductor device technologies”, J. Appl. Phys. vol. 76, pp. 1363-1398, Aug. 1994.
[8]M. K. Kelly, R. P. Vaudo, V. M. Phanse, L. Gorgens, O. Ambacher, and M. Stutzmann, “Large Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy and Laser-Induced Litoff”, Jpn. J. Appl. Phys. vol. 38, pp. L217-L219, Feb. 1999.
[9] C. R. Miskys, M. K. Kelly, O. Ambacher, and M. Stutzmann, “Freestanding GaN- substrates and devices”, Phys. Stat. Sol. (c), vol. 0, pp. 1627-1650, Sep. 2003.
[10] W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L.T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off”, Appl. Phys. Lett., vol. 75, pp. 1360-1362, Sep. 1999.
[11] M. K. Kelly, O. Ambacher, B. Dahlheimer, G. Groos, R. Dimitrov, H. Angerer, and M. Stutzmann, “Optical patterning of GaN films”, Appl. Phys. Lett., vol. 69, pp. 1749-1751, Sep. 1996.
[12] W. S. Wong, T. Sands, and N. W. Cheung, “Damage-free separation of GaN thin films from sapphire substrates”, Appl. Phys. Lett., vol. 72, pp. 599-601, Feb. 1998.
[13] L. Rayleigh, Proc. Phys. Soc. A, vol. 156, pp.326-, 1936.
[14] M. Shimbo, K. Furukawa, K. Fukuda, and K. Tanzawa, “Silicon-to-silicon direct bonding method”, J. Appl. Phys., vol. 60, pp. 2987-2989, Oct. 1986.
[15] J. B. Lasky, “Wafer bonding for silicon-on-insulator technologies”, Appl. Phys. Lett., vol. 48, pp. 78-80, Jan. 1986.
[16] P. W. Barth, Sens. Actuators A, 21±23, p. 91, 1990.
[17] J. Haisma, B. A. C. M. Spierings, U. K. P. Biermann, and A. A. Van Gorkum, “Diversity and feasibility of direct bonding: a survey of dedicated optical technology”, Appl. Opt., vol. 33, pp. 1154-1157, 1994.
[18] Q. Y. Tong, and U. Gösele, “Semiconductor wafer bonding: recent developments”, Mater. Chem. Phys., vol. 37, pp. 101-127, Mar. 1994.
[19] Q. Y. Tong and U. Gösele, “Semiconductor Wafer Bonding: Science and Technology”, Wiley and Sons, 1999.
[20] A. Plöbl and G. Kraüter, “Wafer direct bonding: tailoring adhesion between brittle materials”, Materials Science and Engineering, vol. 25, pp.1-88, Mar. 1999.
[21] Y. Cho and N. W. Cheung, “Low Temperature Si direct bonding by plasma activation for fabrication of MEMS devices”, Mat. Res. Soc. Proc., vol. 657, pp. EE9.2.1-9.1.6, 2001.
[22] W. S. Wong, A. B. Wengrow, Y. Cho, A. Salleo, N. J. Quintoriano, N. W. Cheung, and T. Sands “Integration of GaN Thin Films with Dissimilar Substrate Materials by Pd-In Metal Bonding and Laser Liftoff”, Journal of Electronic Materials”, Vol. 28, pp. 1409-1413, 1999.
[23] W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “InxGa1-xN light emitting diodes on Si substrates fabricated by Pd-In metal bonding and laser lift-off”, Appl. Phys. Lett., vol. 77, pp. 2822-2824, Oct. 2000.
[24] J. Jasinski, Z. Liliental-Weber, S. Estrada, and E. Hu, “Microstructure of GaAs/GaN interfaces produced by direct wafer fusion”, Appl. Phys. Lett., vol. 81, pp. 3152-3154, Oct. 2002.
[25] W. S. Wong, M. Kneissl, P. Mei, D. W. Treat, M. Teepe, and N. M. Johnson, “Continuous-wave InGaN multiple-quantum-well laser diodes on Cupper substrates”, Appl. Phys. Lett. vol. 78, pp. 1198-1200, Feb. 2001.
[26] Z. S. Luo, Y. Cho, V. Loryuenyong, T. Sands, N. W. Cheung, and M. C. Yoo, “Enhancement of (In,Ga)N light-emitting diode performance by laser liftoff and transfer from sapphire to silicon”, IEEE Photonics Technol. Lett., vol. 14, pp. 1400-1402, Oct. 2002.
[27] W. S. Wong, M. Kneissl, D. W. Treat, M. Teepe, N. Miyashita, A. Salleo, and N. M. Johnson, “Continuous-wave InGaN laser diodes on copper and diamond substrates”, J. Mater. Res., vol. 17, pp. 890-894, Apr. 2002.
[28] C. F. Chu, C. C. Yu, H. C. Cheng, C. F. Lin, and S. C. Wang, “Comparison of p-Side Down and p-Side Up GaN Light-Emitting Diodes Fabricated by Laser Lift-Off “, Jpn. J. Appl. Phys. vol. 42, pp. L147-L150, Feb. 2003.
[29] B. S. Tan, S. Yuan, and X. J. Kang, “Performance enhancement of InGaN light-emitting diodes by laser lift-off and transfer from sapphire to copper substrate”, Appl. Phys. Lett., vol. 84, pp. 2757-2759, Apr. 2004.
[30] 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., vol. 84, pp. 855-857, Feb. 2004.
[31] D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highlt efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure”, Appl. Phys. Lett., vol. 86, 052108, pp. 1-3, Jan. 2005.
[32] M. Braunovic, “Fretting in nickel-coated aluminium conductors”, Proceedings of the Thirty-Sixth IEEE Holm and the Fifteenth International Conference on Electrical Contacts, vol. 461, pp. 461-471, Aug. 1990.
[33] Huh C, Lee K S, Kang E J and Park S J, “Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface”, J. Appl. Phys., vol. 93, pp. 9383-9385, June 2003.
[34] H. W. Huang, J. T. Chu1, C. C. Kao, T. H. Hseuh, T. C. Lu, H. C. Kuo, S. C.Wang, and C. C. Yu, “Enhanced light output of an InGaN/GaN light emitting diode with a nano-roughened p-GaN surface”, Nanotechnology, vol. 16, pp. 1844-1848, July 2005.
[35] O. B. Shchekin,a_ 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., vol. 89, 071109, pp. 1-3, Aug. 2006.
[36] M. Stutzmann, O. Ambacher, M. Eickhoff, U. Karrer, A. Lima Pimenta, R. Neuberger, J. Schalwig, R. Dimitrov, P. J. Schuck, and R. D. Grober, “Playing with Polarity”, Phys. Stat. Sol.(b), vol. 228, pp. 505-512, Nov. 2001.
[37] D. Zhuang, and J. H. Edgar, “Wet etching of GaN, AlN, and SiC: a review”, Materials Science and Engineering: R: Report, vol. 48, pp. 1–46, Jan. 2005.
[38] C. Youtsey, I. Adesida, G. Bulman, “Highly anisotropic photoenhanced wet etching of n-type GaN”, Appl. Phys. Lett., vol. 71, pp. 2151-2153, Oct. 1997.
[39] M. S. Minsky, M. White, E. L. Hu, “Room-temperature photoenhanced wet etching of GaN”, Appl. Phys. Lett., vol. 68, pp. 1531-1533, Mar. 1996.
[40] J. K. Ho, C. S. Jong, C. C. Chiu, C. N. Huang, C. Y. Chen, and K. K. Shih, “Low-resistance ohmic contacts to p-type GaN”, Appl. Phys. Lett., vol. 74, pp. 1275-1277, Mar. 1999.
[41] Y.C. Lin, S.J. Chang, Y.K. Su, C.S. Chang, S.C. Shei, J.C. Ke, H.M. Lo, S.C. Chen, and C.W. Kuo, “High power nitride based light emitting diodes with Ni/ITO p-type contacts”, Solid-State Electronics, vol. 47, pp. 1565–1568, Sep. 2003.
[42] K. M. Uang, S. J. Wang, S. L. Chen, C. K. Wu, S. C. Chang, T. M. Chen, and B. W. Liou, “High-Power GaN-Based Light-Emitting Diodes with Transparent Indium Zinc Oxide Films”, Jpn. J. Appl. Phys. vol. 44, pp. 2516- 2519, Apr. 2005.
[43] C. H. Kuo, S. J. Chang, Y. K. Su, R. W. Chuang, C. S. Chang, L. W. Wu, W. C. Lai, J. F. Chen, J. K. Sheu, H. M. Lo, J. M. Tsai, “Nitride-based near-ultraviolet LEDs with an ITO transparent contact”, Materials Science and Engineering B, vol. 106, pp. 69-72, Jan. 2004.
[44] C. J. Tun, J. K. Sheu, B. J. Pong, M. L. Lee, M. Y. Lee, C. K. Hsieh, C. C. Hu, and G. C. Chi, “Enhanced Light Output of GaN-Based Power LEDs With Transparent Al-Doped ZnO Current Spreading Layer”, IEEE Photonics Technol. Lett., vol. 18, pp. 274-276, Jan. 2006.
[45] E. F. Schubert, “Light-Emitting Diodes”, Cambridge University, 2003.
[46] C. Huh, J. M. Lee, D. J. Kim, and S. J. Park, “Improvement in light-output efficiency of InGaN/GaN multiple-quantum well light-emitting diodes by current blocking layer”, J. Appl. Phys., vol. 92, pp. 2248-2250, Sep. 2002.

Chapter 3:
[1] H. Ishikawa, N. Nakada, M. Nakaji, G. Y. Zhao, T. Egawa, T. Jimbo, and M. Umeno, “Investigations on Strained AlGaN/GaN/Sapphire and GaInN Multi-Quantum-Well Surface LEDs Using AlGaN/GaN Bragg Reflectors”, IEICE Trans. Electron., vol.E83-C, pp. 591-597, Apr. 2000.
[2] H. X. Jiang, S. X. Jin, J. Li, J. Shakya, and J. Y. Lin, ”III-nitride blue microdisplays”, Appl. Phys. Lett., vol. 78, pp. 1303-1305, Feb. 2001.
[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., vol. 84, pp. 855-857, Feb. 2004.
[4] D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highlt efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure”, Appl. Phys. Lett., vol. 86, 052108, pp. 1-3, Jan. 2005.
[5] 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., vol. 78, pp. 3379-3381, May 2001.
[6] W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L.T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off”, Appl. Phys. Lett., vol. 75, pp. 1360-1362, Sep. 1999.
[7] A. Motayed, M. Jah, A. Sharma, W. T. Anderson, C. W. Litton, and S. Noor Mohammad, “Two-step surface treatment technique: Realization of nonalloyed low-resistance Ti/Al/Ti/Au ohmic contact to n-GaN”, J. Vac. Sci. Technol. B, vol. 22, pp. 663-667, Mar. 2004.
[8] S. Noor Mohammad, “Contact mechanisms and design principles for nonalloyed ohmic contacts to n-GaN”, J. Appl. Phys., vol. 95, pp. 4856-4865, May 2004.

Chapter 4:
[1] Y. C. Lin, S. J. Chang, Y. K. Su, C. S. Chang, S. C. Shei, J. C. Ke, H. M. Lo, S. C. Chen, and C. W. Kuo, “High power nitride based light emitting diodes with Ni/ITO p-type contacts”, Solid-State Electronics, vol. 47, pp. 1565–1568, Sep. 2003.
[2] H. X. Jiang, S. X. Jin, J. Li, J. Shakya, and J. Y. Lin, ”III-nitride blue microdisplays”, Appl. Phys. Lett., vol. 78, pp. 1303-1305, Feb. 2001.
[3] 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., vol. 78, pp. 3379-3381, May 2001.
[4] W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L.T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off”, Appl. Phys. Lett., vol. 75, pp. 1360-1362, Sep. 1999.
[5] R. H. Horng, C. E. Lee, S. C. Hsu, S. H. Huang, C. C. Wu, C. Y. Kung, and D. S. Wuu, “High-power GaN light-emitting diodes with patterned copper substrates by electroplating”, Phys. Stat. Sol. (a), vol. 201, pp. 2786-2790, Sep. 2004.
[6] 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., vol. 84, pp. 855-857, Feb. 2004.
[7] S. J. Wang, S. L. Chen, K. M. Uang, Y. C. Yang, T. M. Chen, and B. W. Liou, “Effect of Surface Treatment on the performances of Vertical-structured GaN-based LEDs with Electroplating Metallic Substrate”, Proceedings of 63th Device Research Conference, Santa Barbara, USA, June 2005.
[8] D. W. Kim, H. Y. Lee, M. C. Yoo, and G. Y. Yeom, “Highlt efficient vertical laser-liftoff GaN-based light-emitting diodes formed by optimization of the cathode structure”, Appl. Phys. Lett., vol. 86, 052108, pp. 1-3, Jan. 2005.
[9] S. J. Wang, K. M. Uang, S. L. Chen, Y. C. Yang, S. C. Chang, T. M. Chen, and C. H. Chen, “Use of patterned laser liftoff process and electroplating nickel layer for the fabrication of vertical-structured GaN-based light-emitting diodes”, Appl. Phys. Lett., vol. 87, 011111, pp. 1-3, July 2005.
[10] K. M. Uang, S. J. Wang, S. L. Chen, Y. C. Yang, T. M. Chen and B. W. Liou, “Effect of Surface Treatment on the Performance of Vertical-Structure GaN-Based High-Power Light-Emitting Diodes with Electroplated Metallic Substrates”, Jpn. J. Appl. Phys., vol. 45, pp. 3436-3441, Apr. 2006.
[11] C. H. Kuo, S. J. Chang, Y. K. Su, R. W. Chuang, C. S. Chang, L. W. Wu, W. C. Lai, J. F. Chen, J. K. Sheu, H. M. Lo, J. M. Tsai, “Nitride-based near-ultraviolet LEDs with an ITO transparent contact”, Materials Science and Engineering B, vol. 106, pp. 69-72, Jan. 2004.
[12] J. H. Lim, D. K. Hwang, H. S. Kim, J. Y. Oh, J. H. Yang, R. Navamathavan, and S. J. Park, “Low-resistivity and transparent indium-oxide-doped ZnO ohmic contact to p-type GaN”, Appl. Phys. Lett., vol. 85, pp. 6191-6193, Dec. 2004.
[13] R. H. Horng, C. C. Yang, J. Y. Wu, S. H. Huang, C. E. Lee, and D. S. Wuu, “GaN-based light-emitting diodes with indium tin oxide texturing window layers using natural lithography”, Appl. Phys. Lett., vol. 86, 221101, pp. 1-3, May 2005.
[14] T. Minami, “Transparent and conductive multicomponent oxide films prepared by magnetron sputtering”, J. Vac. Sci. Technol. A, vol. 17, pp. 1765-1772, July 1999.
[15] S. P. Jung, C. H. Lin, H. M. Chan, Z. Fan, J. G.. Lu, and H. P. Lee, “High transparency low resistance oxidized Ni/Au–ZnO contacts to p-GaN for high performance LED applications”, Phys. Stat. Sol. (a), vol. 201, pp. 2827-2830, Sep. 2004.
[16] A. Motayed, M. Jah, A. Sharma, W. T. Anderson, C. W. Litton, and S. Noor Mohammad, “Two-step surface treatment technique: Realization of nonalloyed low-resistance Ti/Al/Ti/Au ohmic contact to n-GaN”, J. Vac. Sci. Technol. B, vol. 22, pp. 663-667, Mar. 2004.
[17] S. Noor Mohammad, “Contact mechanisms and design principles for nonalloyed ohmic contacts to n-GaN”, J. Appl. Phys., vol. 95, pp. 4856-4865, May 2004.

Chapter 5:
[1] 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., vol. 78, pp. 3379-3381, May 2001.
[2] Y. C. Lin, S. J. Chang, Y. K. Su, C. S. Chang, S. C. Shei, J. C. Ke, H. M. Lo, S. C. Chen, and C. W. Kuo, “High power nitride based light emitting diodes with Ni/ITO p-type contacts”, Solid-State Electronics, vol. 47, pp. 1565–1568, Sep. 2003.
[3] W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L.T. Romano, and N. M. Johnson, “Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off”, Appl. Phys. Lett., vol. 75, pp. 1360-1362, Sep. 1999.
[4] 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., vol. 84, pp. 855-857, Feb. 2004.
[5] W. Y. Lin, D. S. Wuu, K. F. Pan, S. H. Huang, C. E. Lee, W. K. Wang, S. C. Hsu, Y. Y. Su, S. Y. Huang, and R. H. Horng, “High-Power GaN–Mirror–Cu Light-Emitting Diodes for Vertical Current Injection Using Laser Liftoff and Electroplating Techniques”, IEEE Photon. Technol. Lett., vol. 17, pp. 1809-1811, Sep. 2005.
[6] S. J. Wang, K. M. Uang, S. L. Chen, Y. C. Yang, S. C. Chang, T. M. Chen, and C. H. Chen, “Use of patterned laser liftoff process and electroplating nickel layer for the fabrication of vertical-structured GaN-based light-emitting diodes”, Appl. Phys. Lett., vol. 87, 011111, pp. 1-3, July 2005.
[7] S. J. Wang, S. L. Chen, K. M. Uang, Y. C. Yang, T. M. Chen, and B. W. Liou, “Effect of Surface Treatment on the performances of Vertical-structured GaN-based LEDs with Electroplating Metallic Substrate”, Proceedings of 64th Device Research Conference, Penn State University, University Park, Pennsylvania, USA, June 2006.
[8] K. M. Uang, S. J. Wang, S. L. Chen, Y. C. Yang, T. M. Chen and B. W. Liou, “Effect of Surface Treatment on the Performance of Vertical-Structure GaN-Based High-Power Light-Emitting Diodes with Electroplated Metallic Substrates”, Jpn. J. Appl. Phys., vol. 45, pp. 3436-3441, Apr. 2006.
[9] R. H. Horng, C. C. Yang, J. Y. Wu, S. H. Huang, C. E. Lee, and D. S. Wuu, “GaN-based light-emitting diodes with indium tin oxide texturing window layers using natural lithography”, Appl. Phys. Lett., vol. 86, 221101, pp. 1-3, May 2005.
[10] C. Huh, K. S. Lee, E. J. Kang, and S. J. Park, “GaN-based light-emitting diodes with indium tin oxide texturing window layers using natural lithography”, J. Appl. Phys., vol. 93, pp. 9383-9385, June 2003.