LED照明元件朝向輕薄、小尺寸及高亮度的方向發展，若希望藉由在晶片中注入高電流獲得高亮度，操作溫度會隨之升高而造成電極電性退化，影響LED元件使用年限，因此本研究中將具熱穩定性的超奈米晶鑽石(UNCD)薄膜成長於氮化鎵(GaN)做為電極，研究其成長及光電特性。在研究中分別優化un-doped UNCD及N-doped UNCD製程參數，在成長un-doped UNCD時，藉由光放射光譜(OES)可以觀察到在473、516及563 nm處三支明顯的C2自由基特徵峰，而在拉曼光譜中可以發現UNCD成長於GaN薄膜時具有二階段的成長模式，會先沉積一定密度的石墨相碳原子後轉為沉積UNCD聚合物，而腔體壓力須高於80 torr時才會沉積UNCD；在成長N-doped UNCD時，在OES光譜中除了可以觀察到C2自由基特徵峰外，可以在387 nm及421 nm兩處額外發現CN鍵特徵峰，而所沉積的N-doped UNCD薄膜經拉曼光譜分析後得知，在CH4/Ar電漿中摻雜N2可以提升UNCD薄膜中sp2碳原子的比例，並可以在15 sccm N2的條件下，使N-doped UNCD薄膜的電阻率下降到約2× 106 Ω·cm。隨後將N-doped UNCD薄膜直接沉積於LED上做為電極，通入30-90 mA的電流時可以順利得到LED之電致發光(EL)光譜，在注入80 mA時LED可得到最高亮度，波長位置在458.4 nm，FWHM為20.94 nm，得到EL光譜證實LED的發光層在沉積N-doped UNCD的製程過程中並未遭受破壞。

LED devices are moving toward thin, small size and high brightness. If you want to achieve high brightness by injecting high current into the wafer, the operating temperature will increase. The high operating temperature decreases the life time of LED devices. In this study, ultrananocrystalline diamond (UNCD) thin films, which are thermal stable, are grown on gallium nitride (GaN) as an electrode and study its growth and photoelectronic properties. The un-doped UNCD and N-doped UNCD growth parameters are optimized respectively. The optical emission spectroscopy (OES) indicates that the characteristic peaks at 472, 516 and 563 nm for C2 radical generated in CH4/Ar plasma. The Raman spetrum indicates the two step deposition of UNCD, which the graphite buffer layer should be deposited on GaN thin films first and then UNCD grows on that. The UNCD could be deposited when the chamber pressure might be higher than 80 torr. The OES of CH4/N2/Ar plasma indicates additional CN characteristic peak at 387 nm and 421 nm. The N-doped UNCD thin films are analyzed by Raman spectroscopy and the result indicates that adding N2 in CH4/Ar plasma could increase the concentration of sp2 carbon atoms in the thin films. The resistivity of N-doped UNCD thin films could be decreased to about 2× 106 Ω·cm by adding 15 sccm N2. Then, N-doped UNCD thin films are directly deposited on LED as an electrode. The electroluminescence (EL) spectrum of LED are finished with applying 30-90 mA, and the highest luminance of LED are found with applying 80 mA. The wavelength of luminance is 458.4 nm and FWHM is 20.94 nm. The EL spectrum of LED confirms the emissivet layer in LED is not be damaged during the process of growth N-doped UNCD.

[1] M.Meneghini, L. R.Trevisanello, U.Zehnder, G.Meneghesso, andE.Zanoni, “Reversible degradation of ohmic contacts on p-GaN for application in high-brightness LEDs,” IEEE Trans. Electron Devices, vol. 54, no. 12, pp. 3245–3251, 2007.
[2] H.Zeng et al., “Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system,” Carbon N. Y., vol. 84, no. 1, pp. 103–117, 2015.
[3] T.Dalgleish et al., Synthesis, Properties and Applications of Ultrananocrystalline Diamond, vol. 136, no. 1. 2007.
[4] J. J.Gracio, Q. H.Fan, andJ. C.Madaleno, “Diamond growth by chemical vapour deposition,” J. Phys. D. Appl. Phys., vol. 43, no. 37, 2010.
[5] E. G.Lundblad, “High pressure synthesis of diamond in Sweden in 1953,” AIP Conf. Proc., vol. 309, no. 1, pp. 503–506, 1994.
[6] Y.Gurbuz, O.Esame, I.Tekin, W. P.Kang, andJ. L.Davidson, “Diamond semiconductor technology for RF device applications,” Solid. State. Electron., vol. 49, no. 7, pp. 1055–1070, 2005.
[7] H.Liu andD. S.Dandy, “Studies on nucleation process in diamond CVD: an overview of recent developments,” Diam. Relat. Mater., vol. 4, no. 10, pp. 1173–1188, 1995.
[8] F. J.Zerilli andH. D.Jones, “Surface energy and the size of diamond crystals,” AIP Conf. Proc., vol. 370, no. 1996, p. 163, 1996.
[9] J. E.Butler andA.V.Sumant, “The CVD of nanodiamond materials,” Chem. Vap. Depos., vol. 14, no. 7–8 SPEC. ISS., pp. 145–160, 2008.
[10] D.Pradhan andI. N.Lin, “Effect of titanium powder assisted surface pretreatment process on the nucleation enhancement and surface roughness of ultrananocrystalline diamond thin films,” Appl. Surf. Sci., vol. 255, no. 15, pp. 6907–6913, 2009.
[11] Y.Chakk, R.Brener, and a.Hoffman, “Enhancement of diamond nucleation by ultrasonic substrate abrasion with a mixture of metal and diamond particles,” Appl. Phys. Lett., vol. 66, no. 21, p. 2819, 1995.
[12] Y. C.Chen et al., “Synthesis and characterization of smooth ultrananocrystalline diamond films via low pressure bias-enhanced nucleation and growth,” Appl. Phys. Lett., vol. 92, no. 13, pp. 2–5, 2008.
[13] A.Vul, M.Baidakova, andA.Dideikin, “Nanocrystalline diamond,” Nanomater. Handbook, Second Ed., vol. 20, no. 5–6, pp. 351–378, 2011.
[14] J. E.Butler, R. L.Woodin, L. M.Brown, andP.Fallon, “Thin Film Diamond Growth Mechanisms [and Comment],” Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., vol. 342, no. 1664, pp. 209–224, 1993.
[15] C. J.Rennick et al., “Improved characterisation of C2and CH radical number density distributions in a DC arc jet used for diamond chemical vapour deposition,” Diam. Relat. Mater., vol. 13, no. 4–8, pp. 561–568, 2004.
[16] P. C.Redfern, D. A.Horner, L. A.Curtiss, andD. M.Gruen, “Theoretical Studies of Growth of Diamond (110) from Dicarbon †,” J. Phys. Chem., vol. 100, no. 28, pp. 11654–11663, 1996.
[17] D. M.Gruen, S.Liu, A. R.Krauss, J.Luo, andX.Pan, “Fullerenes as precursors for diamond film growth without hydrogen or oxygen additions,” Appl. Phys. Lett., vol. 64, no. 12, pp. 1502–1504, 1994.
[18] D.Zhou, T. G.McCauley, L. C.Qin, A. R.Krauss, andD. M.Gruen, “Synthesis of nanocrystalline diamond thin films from an Ar-CH4 microwave plasma,” J. Appl. Phys., vol. 83, no. 1, pp. 540–543, 1998.
[19] D.Zhou, D. M.Gruen, L. C.Qin, T. G.McCauley, andA. R.Krauss, “Control of diamond film microstructure by Ar additions to CH4/H2microwave plasmas,” J. Appl. Phys., vol. 84, no. 4, pp. 1981–1989, 1998.
[20] H.Zhou, J.Watanabe, M.Miyake, A.Ogino, M.Nagatsu, andR.Zhan, “Optical and mass spectroscopy measurements of Ar/CH4/H2microwave plasma for nano-crystalline diamond film deposition,” Diam. Relat. Mater., vol. 16, no. 4–7 SPEC. ISS., pp. 675–678, 2007.
[21] J. R.Rabeau, P.John, J. I. B.Wilson, andY.Fan, “The role of C2in nanocrystalline diamond growth,” J. Appl. Phys., vol. 96, no. 11, pp. 6724–6732, 2004.
[22] M.Ecken, E.Neyts, andA.Bogaerts, “Molecular dynamics simulations of the sticking and etch behavior of various growth species of (ultra)nanocrystalline diamond films,” Chem. Vap. Depos., vol. 14, no. 7–8 SPEC. ISS., pp. 213–223, 2008.
[23] G.Lombardi, K.Hassouni, F.Bénédic, F.Mohasseb, J.Röpcke, andA.Gicquel, “Spectroscopic diagnostics and modeling of Ar/H2/CH4 microwave discharges used for nanocrystalline diamond deposition,” J. Appl. Phys., vol. 96, no. 11, pp. 6739–6751, 2004.
[24] A.Misra et al., “Hexagonal diamond synthesis on h-GaN strained films,” Appl. Phys. Lett., vol. 89, no. 7, pp. 1–4, 2006.
[25] G. W. G.vanDreumel et al., “Growth of GaN on nano-crystalline diamond substrates,” Diam. Relat. Mater., vol. 18, no. 5–8, pp. 1043–1047, 2009.
[26] I. I.Vlasov, V. G.Ralchenko, E.Goovaerts, A.V.Saveliev, andM.V.Kanzyuba, “Bulk and surface-enhanced Raman spectroscopy of nitrogen-doped ultrananocrystalline diamond films,” Physica Status Solidi (A) Applications and Materials Science, vol. 203, no. 12. pp. 3028–3035, 2006.
[27] M.Oba andT.Sugino, “Growth of (111)-oriented diamond grains on hexagonal GaN,” Jpn. J. Appl. Phys., vol. 39, no. 12 A, 2000.
[28] P. W.May, H. Y.Tsai, W. N.Wang, andJ. A.Smith, “Deposition of CVD diamond onto GaN,” Diam. Relat. Mater., vol. 15, no. 4–8, pp. 526–530, 2006.
[29] Y. S.Zou et al., “Chemical vapor deposition of diamond films on patterned GaN substrates via a thin silicon nitride protective layer,” Cryst. Growth Des., vol. 8, no. 5, pp. 1770–1773, 2008.
[30] V.Goyal, A.V.Sumant, D.Teweldebrhan, andA. A.Balandin, “Direct low-temperature integration of nanocrystalline diamond with GaN substrates for improved thermal management of high-power electronics,” Adv. Funct. Mater., vol. 22, no. 7, pp. 1525–1530, 2012.
[31] M.Nazari et al., “Near-ultraviolet micro-Raman study of diamond grown on GaN,” Appl. Phys. Lett., vol. 108, no. 3, 2016.
[32] T.Izak et al., “Selective area deposition of diamond films on AlGaN/GaN heterostructures,” Phys. Status Solidi Basic Res., vol. 251, no. 12, pp. 2574–2580, 2014.
[33] O.Babchenko et al., “Study on electronic properties of diamond/SiNx-coated AlGaN/GaN high electron mobility transistors operating up to 500 °C,” Diam. Relat. Mater., vol. 89, no. September, pp. 266–272, 2018.
[34] J. L.Liu, H. M.Tian, L. X.Chen, J. J.Wei, L. F.Hei, andC. M.Li, “Preparation of nano-diamond films on GaN with a Si buffer layer,” Xinxing Tan Cailiao/New Carbon Mater., vol. 31, no. 5, pp. 518–524, 2016.
[35] S.Mandal et al., “Surface Zeta Potential and Diamond Seeding on Gallium Nitride Films,” ACS Omega, vol. 2, no. 10, pp. 7275–7280, 2017.
[36] A.Bar-Cohen, J. J.Maurer, andA.Sivananthan, “Near-junction microfluidic thermal management of RF power amplifiers,” in 2015 IEEE International Conference on Microwaves, Communications, Antennas and Electronic Systems, COMCAS 2015, 2015, no. November, pp. 2–4.
[37] C. J. H.Wort andR. S.Balmer, “Diamond as an electronic material,” Mater. Today, vol. 11, no. 1–2, pp. 22–28, 2008.
[38] J.V.Macpherson, “A practical guide to using boron doped diamond in electrochemical research,” Phys. Chem. Chem. Phys., vol. 17, no. 5, pp. 2935–2949, 2015.
[39] S.Bhattacharyya et al., “Synthesis and characterization of highly-conducting nitrogen-doped ultrananocrystalline diamond films,” Appl. Phys. Lett., vol. 79, no. 10, pp. 1441–1443, 2001.
[40] J.Birrell, J. E.Gerbi, O.Auciello, J. M.Gibson, D. M.Gruen, andJ. A.Carlisle, “Bonding structure in nitrogen doped ultrananocrystalline diamond,” J. Appl. Phys., vol. 93, no. 9, pp. 5606–5612, 2003.
[41] O. A.Williams, S.Curat, J. E.Gerbi, D. M.Gruen, andR. B.Jackman, “N-Type Conductivity in Ultrananocrystalline Diamond Films,” Appl. Phys. Lett., vol. 85, no. 10, pp. 1680–1682, 2004.
[42] P.Achatz, O. A.Williams, P.Bruno, D. M.Gruen, J. A.Garrido, andM.Stutzmann, “Effect of nitrogen on the electronic properties of ultrananocrystalline diamond thin films grown on quartz and diamond substrates,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 74, no. 15, pp. 3–9, 2006.
[43] K. J.Sankaran et al., “Structural and electrical properties of conducting diamond nanowires,” ACS Appl. Mater. Interfaces, vol. 5, no. 4, pp. 1294–1301, 2013.
[44] R.Arenal, P.Bruno, D. J.Miller, M.Bleuel, J.Lal, andD. M.Gruen, “Diamond nanowires and the insulator-metal transition in ultrananocrystalline diamond films,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 75, no. 19, pp. 1–11, 2007.
[45] G.Haacke, “New figure of merit for transparent conductors,” J. Appl. Phys., vol. 47, no. 9, pp. 4086–4089, 1976.
[46] P. T.Joseph, N. H.Tai, Y. C.Chen, H. F.Cheng, andI. N.Lin, “Transparent ultrananocrystalline diamond films on quartz substrate,” Diam. Relat. Mater., vol. 17, no. 4–5, pp. 476–480, 2008.
[47] C. R.Lin et al., “Fabrication of highly transparent ultrananocrystalline diamond films from focused microwave plasma jets,” Surf. Coatings Technol., vol. 231, pp. 594–598, 2013.
[48] W.-H.Liao, D.-H.Wei, andC.-R.Lin, “Synthesis of highly transparent ultrananocrystalline diamond films from a low-pressure, low-temperature focused microwave plasma jet.,” Nanoscale Res. Lett., vol. 7, no. 1, p. 82, 2012.
[49] A. C.Ferrari andJ.Robertson, “Raman spectroscopy of amorphous, nanostructured, diamond{\textendash}like carbon, and nanodiamond,” Philos. Trans. R. Soc., A, vol. 362, no. 1824, pp. 2477–2512, 2004.
[50] P. K.Chu andL.Li, “Characterization of amorphous and nanocrystalline carbon films,” Mater. Chem. Phys., vol. 96, no. 2–3, pp. 253–277, 2006.
[51] H.Kuzmany, R.Pfeiffer, N.Salk, andB.Günther, “The mystery of the 1140 cm-1Raman line in nanocrystalline diamond films,” Carbon N. Y., vol. 42, no. 5–6, pp. 911–917, 2004.
[52] J.Kurian, K. J.Sankaran, J. P.Thomas, N. H.Tai, H. C.Chen, andI. N.Lin, “The role of nanographitic phase on enhancing the electron field emission properties of hybrid granular structured diamond films: The electron energy loss spectroscopic studies,” J. Phys. D. Appl. Phys., vol. 47, no. 41, 2014.
[53] Z. C.Feng, W.Wang, S. J.Chua, P. X.Zhang, K. P. J.Williams, andG. D.Pitt, “Raman scattering properties of GaN thin films grown on sapphire under visible and ultraviolet excitation,” J. Raman Spectrosc., vol. 32, no. 10, pp. 840–846, 2001.
[54] C.Liu, X.Gao, D.Tao, J.Wang, andY.Zeng, “Structural, Raman scattering and magnetic characteristics of Er+-implanted GaN thin films,” J. Alloys Compd., vol. 618, pp. 533–536, 2015.
[55] Y.Liu, C.Liu, Y.Chen, Y.Tzeng, P.Tso, andI.Lin, “Effects of hydrogen additive on microwave plasma CVD of nanocrystalline diamond in mixtures of argon and methane,” Diam. Relat. Mater., vol. 13, no. 4–8, pp. 671–678, 2004.
[56] J. H.Jiang, Y. C.Chu, W. C.Fang, S. T.Chen, andY.Tzeng, “Effects of gas residence time on microwave plasma enhanced CVD of ultrananocrystalline diamond in mixtures of methane and argon without hydrogen or oxygen additives,” Diam. Relat. Mater., vol. 24, pp. 153–157, 2012.
[57] C. S.Wang, G. H.Tong, H. C.Chen, W. C.Shih, andI. N.Lin, “Effect of N2addition in Ar plasma on the development of microstructure of ultra-nanocrystalline diamond films,” Diam. Relat. Mater., vol. 19, no. 2–3, pp. 147–152, 2010.
[58] W. C.Ke, F. W.Lee, C. Y.Chiang, Z. Y.Liang, W. K.Chen, andT. Y.Seong, “InGaN-Based Light-Emitting Diodes Grown on a Micro/Nanoscale Hybrid Patterned Sapphire Substrate,” ACS Appl. Mater. Interfaces, vol. 8, no. 50, pp. 34520–34529, 2016.