太陽能與海水是地球上十分豐富的資源，透過半導體的輔助，我們可以將太陽能轉換化學電勢，以此能量對海水進行光電化學反應，生成可以使用之能源。此能源轉換的優點在於其產物為氫氣與甲酸等等綠色能源，且此反應前的反應物(海水)與反應後的產物均非溫室氣體與污染物，相對石油煤氣燃燒後所產生的污染物環保，因此這過程可以視為一個綠色能源，若此技術繼續發展，則可以期待有朝一日成為永續的綠色能源轉換方式。
本篇論文主要探討摻鎂的三五族氮化鎵光電元件用於光電化學反應，一般未摻雜的氮化鎵(undoped Gallium Nitride , u-GaN)因為本身有的缺陷(Nitrogen Vacancy)以及雜質影響等等，會使得未摻雜的氮化鎵變成偏向以電子為主要載子的n型氮化鎵(n-GaN)[1]。在進行光電化學反應時，氮化鎵照光生成電子電洞對，電子隨給予的正偏壓離開氮化鎵到達對電極，而剩下電洞則留在半導體內，從能帶圖可以預知電洞將累積於氮化鎵與電解液接面，因此若電洞沒有順利排出於電解液中，便很容易氧化氮化鎵中的鎵造成光腐蝕現象。因此在本實驗中透過在氮化鎵摻雜鎂，使氮化鎵轉為以電洞為主要載子(p-type)，以此來提升氮化鎵的抗腐蝕功能。實驗中我們利用MOCVD成長氮化鎵，在製程中通入鎂使氮化鎵轉換成以電洞為主要載子的半導體(p-type)，並透過在製程中通入不同濃度的鎂，以此來挑選出最適合的p型氮化鎵(p-GaN)。
因為p型氮化鎵電流偏小，所以我們接著在其上覆蓋一層薄層n型氮化鎵(n-GaN)來提升p型氮化鎵中載子對分離機率，期望透過這步驟來提升p的整體光電流，實驗中我們發現透過這步驟的確有效的提升整體光電流。

In this study, we use p- GaN as working electrode in photoelectrochemical system in order to prevent GaN from corrosion after long time reaction. To some p-GaN sample, we grow a thin film n-GaN on p-GaN , and then we periodical-stripe etch thin film n-GaN to expose p-GaN by Inductively Coupled Plasma Reactive-Ion Etching(ICP-RIE). To other p-GaN samples, we use the ion implantation technique to convert p-GaN to n-GaN. After the process of above, we comparing the photoelectrochemical data and choosing 3 times Mg concentration because the data of original Mg concentration demonstrate a not typical p-GaN characteristic. At the end, we deposit SiO2 on 3 times concentration of Mg p-GaN to get the higher photocuurent and we confirm the low corrosion of GaN from SEM image and Alpha Step data.

[1.] 台灣電力股份有限公司103 年度 研究計畫 546－4305－0301 完成報告
[2.] 國研院政策中心 - 從數據看全球暖化
[3.] J. Lédé, F. Lapicque, J. Villermaux, “ Production of hydrogen by direct thermal decomposition of water,” International Journal of Hydrogen Energy, vol. 8, pp. 675-679.(1983)
[4.] W. Kreuter, H. Hofmann , “ Electrolysis: The important energy transformer in a world of sustainable energy,” International Journal of Hydrogen Energy, vol. 23, pp. 661-666.(1998)
[5.] O.Khaselev, J.A.Turner, “A monolithic photovoltaic photoelectrochemical device for hydrogen production via water splitting,” Science, vol. 280, pp. 425-427.(1998)
[6.] Fujishima, K. Honda, “ Electrochemical photolysis of water at a semiconductor electrode,” Nature, vol. 238, pp. 37-38. (1972)
[7.] Fujishima, K. Kohayakawa, and K. Honda, “ Hydrogen production under sunlight with an electrochemical photocell,” Journal of the Electrochemical Society, vol. 122, pp. 1487-1489. (1975)
[8.] A. J. Nozik, R. Memming, “ Physical chemistry of semiconductor-liquid interfaces,” The Journal of Physical Chemistry, vol. 100, pp. 13061-13078. (1996)
[9.] I. M. Huygens, K. Strubbe, W. P. Gomes, “ Electrochemistry and Photoetching of n-GaN,” Journal of The Electrochemical Society, vol. 147, pp. 1797-1802. (2000)
[10.] Katsushi FUJII, Takeshi KARASAWA and Kazuhiro OHKAWA, “Hydrogen Gas Generation by Splitting Aqueous Water Using n-Type GaN Photoelectrode with Anodic Oxidation,” Japanese Journal of Applied Physics, vol. 44, No. 18, , pp. L 543–L 545. (2005)
[11.] Karsten Müller , Kriston Brooks, and Tom Autrey, “Hydrogen Storage in Formic Acid: A Comparison of Process Options,” Energy Fuels, 31 (11), pp 12603–12611. (2017)
[12.] S. Yotsuhashi, M. Deguchi, Y. Zenitani, R. Hinogami, H. Hashiba, Y. Yamada, K. Ohkawa, “ Photo-induced CO2 Reduction with GaN Electrode in Aqueous System,” Applied Physics Express, vol. 4, p. 117101. (2011)
[13.] M M. J. Kenney, M. Gong, Y. Li, J. Z. Wu, J. Feng, M. Lanza and H. Dai, “High-Performance Silicon Photoanodes Passivated with Ultrathin Nickel Films for Water Oxidation”,Science, vol 342, 836–840. (2013)
[14.] Y. W. Chen, J. D. Prange, S. Duhnen, Y. Park, M. Gunji,C. E. D. Chidsey and P. C. McIntyre, “Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation”, Nature Materials vol 10 , 539–544. (2011)
[15.] A. Paracchino, V. Laporte, K. Sivula, M. Gratzel and E. Thimsen, Nat. Mater., “Highly active oxide photocathode for photoelectrochemical water reduction ” , Nature Materials vol 10 , 456–461. (2011)
[16.] B. Seger, T. Pedersen, A. B. Laursen, P. C. K. Vesborg,O. Hansen and I. Chorkendorff, “ Using TiO2 as a Conductive Protective Layer for Photocathodic H2 Evolution”, J. Am. Chem. Soc. 135, 1057. (2013)
[17.] Wilson A. Smith, Ian D. Sharp, Nicholas C. Strandwitz and Juan Bisquert, “Interfacial band-edge energetics for solar fuels production,” Energy Environ. Sci., 8, 2851—2862. (2015)
[18.] I. M. Huygens, K. Strubbe, and W. P. Gomes, “Electrochemistry and Photoetching of n-GaN,” Journal of The Electrochemical Society, 147 (5) 1797-1802. (2000)
[19.] M. G. Walter, E. L. Warren, J. R. McKone, S. W. Boettcher, Q. Mi, E. A. Santori, andN. S. Lewis, “Solar Water Splitting Cells,” Chem. Rev., vol. 110, no. 11, pp. 6446–6473. (2010)
[20.] Katsushi FUJII and Kazuhiro OHKAWA ,”Photoelectrochemical Properties of p-Type GaN in Comparison with n-Type GaN,” Japanese Journal of Applied Physics, vol. 44, No. 28, pp. L 909–L 911. (2005)
[21.] A. J. Bard, L. R. Faulkner, Eelectrochemical Methods: Fundamentals and Applications, Second Edition, New York: John Wiley & Sons, pp. 2–3. (2001)
[22.] M.G. Kibria , S. Zhao , F.A. Chowdhury , Q. Wang , H.P.T. Nguyen , M.L. Trudeau, H. Guo & Z. Mi, “Tuning the surface Fermi level on p-type gallium nitride nanowires for efficient overall water splitting, ” |Nature Communications,vol 5, Article number: 3825. (2014)
[23.] Joel W. Ager, Matthew R. Shaner, Karl A. Walczak, Ian D. Sharpae and Shane Ardo, ” Experimental demonstrations of spontaneous, solar-driven photoelectrochemical water splitting,” Energy Environ. Sci., 8, 2811. (2015)
[24.] J. Reichman, “The current-voltage characteristics of semiconductor-electrolyte junction photovoltaic cells,” Appl. Phys. Lett. 36(7). (1979)
[25.] Ne’stor Guijarro, Mathieu S. Pre’vot and Kevin Sivula, “Surface modification of semiconductor photoelectrodes, ” Phys. Chem. Chem. Phys., 17, 15655—15674. (2015)
[26.] W. Bott, “ Electrochemistry of Semiconductors,” Curr. Sep., pp. 87-91. (1998)
[27.] S. C. Roy, O. K. Varghese, M. Paulose, and C. A. Grimes, “ Toward Solar Fuels: Photocatalytic Conversion of Carbon Dioxide to Hydrocarbons,”ACS Nano, vol. 4, pp. 1259-1278. (2010)
[28.] A. J. Bard, L. R. Faulkner, “ Eelectrochemical Methods: Fundamentals and Applications”, Second Edition, New York: John Wiley & Sons, pp. 2–3. (2001)
[29.] R. V. D. Krol, and M. Grätzel, “Photoelectrochemical Hydrogen Production”, New York: Springer Press, pp. 75–77. (2012)
[30.] C. A. Grimes, O. K. Varghese, S. Ranjan, Light, Water, Hydrogen: The Solar Generation of Hydrogen by Water Photoelectrolysis, ” | New York: Springer Press, pp. 126–131. (2008)
[31.] Howard Reiss, Adam Heller, “The Absolute Potential of the Standard Hydrogen Electrode: A New Estimate,” J. Phys. Chem.,89, 4207-4213. (1985)
[32.] Shiyou Chen, and Lin-Wang Wang, “Thermodynamic Oxidation and Reduction Potentials of Photocatalytic Semiconductors in Aqueous Solution, ” | Chem. Mater., 24, 3659−3666. (2012)
[33.] 蔣曉白,”半導體積體電路生產技術 從摻雜技術—離子佈植（IonImplantation）談起,” 國家奈米元件實驗室 奈米通訊 Nano Communication ,20卷,No.4
[34.] Präsident der Humboldt-Universität zu Berlin: Prof. Dr. Hans Jürgen Prömel (in Vertretung) Dekan der Mathematisch-Naturwissenschaftlichen Fakultät I: Prof. Thomas Buckhout, PhD, “Optical polarization anisotropy in nonpolar GaN thin films due to crystal symmetry and anisotropic strain”. (2005)
[35.] J. K. Sheu, Y. K. Su, G. C. Chi, B. J. Pong, C. Y. Chen, C. N. Huang, and W. C. Chen,”Photoluminescence spectroscopy of Mg-doped GaN,” Journal of Applied Physics, Vol. 84, No. 8, 15 October (1998)
[36.] Zu-Po Yang, Zhong-Han Xie, Chia-Ching Lin, and Ya-Ju Lee, ”Slanted n-ZnO nanorod arrays/p-GaN lightemitting diodes with strong ultraviolet emissions ” Optical Materials Express 404. (2015)
[37.] M. Smith, G. D. Chen, J. Y. Lin, H. X. Jiang, A. Salvador, B. N. Sverdlov,A. Botchkarev, H. Morkoc, and B. Goldenberg, ”Mechanisms of band‐edge emission in Mg‐doped p‐type GaNAppl, ” Applied Physics Letters, 68, Vol. 68, No. 14. (1996)
[38.] N. Ben Sedrine , T. C. Esteves , J. Rodrigues , L. Rino , M. R. Correia , M. C. Sequeira , A. J. Neves , E. Alves , M. Bockowski , P. R. Edwards, K.P. O’Donnell, K. Lorenz & T. Monteiro, ”Photoluminescence studies of a perceived white light emission from a monolithic InGaN/GaN quantum well structure,” Scientific Reports volume5, Article number: 13739. (2015)
[39.] B AlOtaibi, M Harati, S Fan, S Zhao, H P T Nguyen, M G Kibria and Z Mi, ”High efficiency photoelectrochemical water splitting and hydrogen generation using GaN nanowire photoelectrode,” IOP Publishing Ltd, Nanotechnology 24. (2013)
[40.] Naoki KOBAYASHI , Toru NARUMI and Ryusuke MORITA, ”Hydrogen Evolution from p-GaN Cathode in Water under UV Light Irradiation, ” Japanese Journal of Applied Physics Vol. 44, No. 24, pp. L 784–L 786. (2005)
[41.] Jinn-Kong Sheu, Po-Hsun Liao,a Hsin-Yan Chenga and Ming-Lun Lee,” Photoelectrochemical hydrogen generation from water using undoped GaN with selective-area Siimplanted stripes as a photoelectrode,” J. Mater. Chem. A, 5, 22625–22630.(2017)