摘要:
本論文為利用原子層沉積法(ALD)成長高品質氧化鋁及摻鋁氧化鋅薄膜於n型矽基板來建構一高效率光偵測器之研究。AZO於元件結構中除扮演傳統導電電極之外，亦同時肩負與Si形成光偵測區及導電電極和抗反射層等角色形成一多功能導電電極，此為與傳統金屬導電電極極為不同之處。除此之外亦探討不同薄膜厚度對於此金屬氧化物半導體結構元件之光電轉換效率或光響應的影響。
AZO的功函數(4.6eV)大於n型矽基板(4.2eV)，故會形成一蕭特基能障，並在n型矽基板處產生內建電場，當n型矽基板吸收光而產生電子電洞對時，會因內建電場而有效分離，並累積於氧化鋁與n型矽基板的接面兩側，若於兩者間成長氧化鋁薄膜形成一金氧半結構(Metal-Oxide-Semiconductor Structure)可有效減少漏電流，增加光電轉換效率。
相較於傳統ALD製程，本論文使用氣流中斷法及直接噴灑鋁前驅物進行取代的方式成長摻鋁氧化鋅，所成長的薄膜在極薄的情況下仍然具有良好品質，不會因薄膜太薄而影響到電性，故薄膜可以線性疊加調控至理想厚度，本論文之元件光學特性對於膜厚變化十分敏感
，因此選擇利於調控膜厚的ALD製程。摻鋁氧化鋅的折射係數(n)小於n型矽基板，因此光經由空氣進入AZO薄膜再進入n型矽基板折射率會比直接進入n型矽基板低，故AZO薄膜具有抗反射效果，加上AZO薄膜本身電阻值低，可直接當作抗反射電極使用，且摻鋁氧化鋅及氧化鋁於不同的波長下具有不同的n值，故我們可以藉由調整兩層薄膜之厚度使元件能在特定波長的光源下有最低的反射值，換句話說我們可以製造一低電阻可調控光學薄膜。
由光電壓量測結果得知:於n型矽基板上鍍上摻鋁氧化鋅在405nm雷射光源照射下(光強度0.1mW)可產生0.155V的光電壓，相當於元件有1550V/W的光電轉換效率，在中間加上5nm的氧化鋁可提升光電壓至0.241V，相當於2410V/W光電轉換效率，有氧化鋁在中間阻擋漏電流可增強55%之光電壓，使元件具有高光電傳換效率並成功證實了此元件應用於光感測元件之可行性。

Abstract
In this study, we provide high efficiency photodetector with high quality aluminum doped zinc oxide (AZO) and aluminum oxide (Al2O3) thin film on n-type Si in atomic layer deposition (ALD) The conventional metal electrode just plays the role of carrier collection, having high optical reflection and the trade-off between optical sensing area and metal electrode to impact the optical-to-electrode conversion efficiency further. AZO, is a transparent material, can be the metal electrode with the anti-reflection function under some specific film thickness, except the optical sensing area between AZO and n-type Si. Therefore, the AZO-based electrode include carrier collection, photogeneration and anti-reflection coating simultaneously.
Because of the difference of work function, AZO (4.6eV) and n-type Si (4.2eV), the interface between AZO and n-type Si will be the Schottky Junction for optical sensing, photo-generated and carrier collection. For lower dark carrier in our device, the extra Al2O3 can be prepared over n-type Si in advance to obtain high optical-to-electrical conversion efficiency further in the proposed Metal-Oxide-Semiconductor structure.
Comparing the conventional ALD and this using flow-interruption method with directly spray aluminum precursors, the high quality ultra-thin AZO film can be prepared to the desire thickness for providing the anti-reflection function . The n value diffraction refractive index of AZO and that of Al2O3 is different. The lowest optical reflection in the specific incident light wavelength can achieved by adjusting the film thickness of AZO or that of Al2O3. Therefore, the ALD process is necessary for accuracy film thickness control to obtain adjustable optical thin film and transparent metal electrode simultaneously.
According to the photovoltage measured results(405nm light with intensity of 0.1mW), the photovoltage of 0.155V (1550V/W) and 0.241V (V/W) can be obtained in the device structure (AZO/n-type Si) and in the designed structure (AZO/Al2O3/n-type Si), respectively. The existence of 5nm Al2O3 enhances the photovoltage output around 55% compared with the device without Al2O3. Further, the high optical-to-electrical conversion capability benefits the demanded optical sensing applications.

目錄
第一章 序論 1
1-1 前言 1
1-2 研究動機 2
1-3 元件設計與原理 3
第二章 文獻回顧 4
2-1 光電元件 4
2-1-1 蕭特基接面光二極體 4
2-1-2 P-N接面光二極體 5
2-2 氧化鋅 6
2-2-1 氧化鋅基本材料性質 6
2-2-2 氧化鋅之應用 7
2-2-3 氧化鋅薄膜製程 7
2-2-4 摻鋁氧化鋅 9
2-2-5 摻鋁氧化鋅製程 10
2-3 氧化鋁 11
2-4 原子層沉積(Atomic Layer Deposition, ALD) 12
2-4-1 原子層沉積法原理 12
2-4-2 氣流中斷法 13
2-5 複數折射率 14
第三章 元件製備與驗證 19
3-1 實驗流程 19
3-1-1 背電極製作 20
3-1-2 基板清潔 20
3-1-3 成長AZO及Al2O3薄膜 21
3-1-4 樣品量測 22
3-2 實驗測量儀器 22
3-2-1 X光繞射儀(X-ray Diffraction, XRD) 22
3-2-2 X光反射儀(X-ray Reflectivity, XRR) 23
3-2-3 可見-紫外光光譜(Ultraviolet-visible Spectroscopy) 24
3-2-4 光電特性測量 24
3-2-5 橢圓偏振儀 25
第四章 結果與討論 27
4-1 摻鋁氧化鋅及氧化鋁薄膜材料本質分析 27
4-1-1 摻鋁氧化鋅薄膜材料本質分析 27
4-1-2 氧化鋁薄膜材料本質分析 31
4-2 摻鋁氧化鋅薄膜及元件光學特性分析 31
4-2-1 摻鋁氧化鋅薄膜光學特性分析 31
4-2-2 雙層薄膜元件光學特性分析 33
4-3 雙層薄膜元件光電特性分析 40
第五章 結論 46
參考文獻 48

參考文獻
[1] M. Grätzel, "Photoelectrochemical cells," Nature, vol. 414, p. 338, 11/15/online 2001.
[2] Y. M. Chi et al., "Optimizing surface plasmon resonance effects on finger electrodes to enhance the efficiency of silicon-based solar cells," (in English), Energy & Environmental Science, Article vol. 6, no. 3, pp. 935-942, Mar 2013.
[3] S. J. Jiao et al., "ZnO p-n junction light-emitting diodes fabricated on sapphire substrates," (in English), Applied Physics Letters, Article vol. 88, no. 3, p. 3, Jan 2006, Art. no. 031911.
[4] M. Zeman, R. Van Swaaij, M. Zuiddam, J. W. Metselaar, and R. E. I. Schropp, "Effect of interface roughness on light scattering and optical properties of a-Si : H solar cells," in Amorphous and Heterogeneous Silicon Thin Films: Fundamentals to Devices-1999, vol. 557, H. M. Branz, R. W. Collins, H. Okamoto, S. Guha, and R. Schropp, Eds. (Materials Research Society Symposium Proceedings, Warrendale: Materials Research Society, 1999, pp. 725-730.
[5] Y. M. Chang, M. C. Liu, P. H. Kao, C. M. Lin, H. Y. Lee, and J. Y. Juang, "Field Emission in Vertically Aligned ZnO/Si-Nanopillars with Ultra Low Turn-On Field," (in English), Acs Applied Materials & Interfaces, Article vol. 4, no. 3, pp. 1411-1416, Mar 2012.
[6] R. M. Yu, S. M. Niu, C. F. Pan, and Z. L. Wang, "Piezotronic effect enhanced performance of Schottky-contacted optical, gas, chemical and biological nanosensors," (in English), Nano Energy, Review vol. 14, pp. 312-339, May 2015.
[7] P. H. Yeh, Z. Li, and Z. L. Wang, "Schottky-Gated Probe-Free ZnO Nanowire Biosensor," (in English), Advanced Materials, Article vol. 21, no. 48, pp. 4975-+, Dec 2009.
[8] R. K. Gupta and F. Yakuphanoglu, "Photoconductive Schottky diode based on Al/p-Si/SnS2/Ag for optical sensor applications," (in English), Solar Energy, Article vol. 86, no. 5, pp. 1539-1545, May 2012.
[9] J. Schalwig et al., "Hydrogen response mechanism of Pt-GaN Schottky diodes," (in English), Applied Physics Letters, Article vol. 80, no. 7, pp. 1222-1224, Feb 2002.
[10] S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, and T. Steiner, "Recent progress in processing and properties of ZnO," (in English), Superlattices and Microstructures, Review vol. 34, no. 1-2, pp. 3-32, Jul-Aug 2003.
[11] M. Ichimura and Y. Maeda, "Heterojunctions based on photochemically deposited CuxZnyS and electrochemically deposited ZnO," (in English), Solid-State Electronics, Article vol. 107, pp. 8-10, May 2015.
[12] Z. N. Wang et al., "Optimizing Performance of Silicon-Based p-n junction Photodetectors by the Piezo-Phototronic Effect," (in English), Acs Nano, Article vol. 8, no. 12, pp. 12866-12873, Dec 2014.
[13] P. L. Chen et al., "INTEGRATED SILICON MICROBEAM PI-FET ACCELEROMETER," (in English), Ieee Transactions on Electron Devices, Article vol. 29, no. 1, pp. 27-33, 1982.
[14] G. K. Mani and J. B. B. Rayappan, "A highly selective room temperature ammonia sensor using spray deposited zinc oxide thin film," (in English), Sensors and Actuators B-Chemical, Article vol. 183, pp. 459-466, Jul 2013.
[15] N. D. Khoang et al., "On-chip growth of wafer-scale planar-type ZnO nanorod sensors for effective detection of CO gas," (in English), Sensors and Actuators B-Chemical, Article vol. 181, pp. 529-536, May 2013.
[16] C. W. Zou, F. Liang, and S. W. Xue, "Synthesis and oxygen vacancy related NO2 gas sensing properties of ZnO:Co nanorods arrays gown by a hydrothermal method," (in English), Applied Surface Science, Article vol. 353, pp. 1061-1069, Oct 2015.
[17] M. L. Yin and S. Z. Liu, "One-pot synthesis of Co-doped ZnO hierarchical aggregate and its high gas sensor performance," (in English), Materials Chemistry and Physics, Article vol. 149, pp. 344-349, Jan 2015.
[18] B. Q. Cao, X. L. Hu, H. M. Wei, and H. Y. Xu, "Radial and Axial Nanowire Heterostructures Grown with ZnO Nanowires as Templates," in Tencon 2010: 2010 Ieee Region 10 Conference, T. Okado, K. Araki, and H. Nishino, Eds. (TENCON IEEE Region 10 Conference Proceedings, New York: Ieee, 2010, pp. 986-989.
[19] M. Ahmad, H. Y. Sun, and J. Zhu, "Enhanced Photoluminescence and Field-Emission Behavior of Vertically Well Aligned Arrays of In-Doped ZnO Nanowires," (in English), Acs Applied Materials & Interfaces, Article vol. 3, no. 4, pp. 1299-1305, Apr 2011.
[20] R. X. Shi, P. Yang, X. B. Dong, Q. Ma, and A. Y. Zhang, "Growth of flower-like ZnO on ZnO nanorod arrays created on zinc substrate through low-temperature hydrothermal synthesis," (in English), Applied Surface Science, Article vol. 264, pp. 162-170, Jan 2013.
[21] S. J. Wang, C. S. Song, K. Cheng, S. X. Dai, Y. Y. Zhang, and Z. L. Du, "Controllable growth of ZnO nanorod arrays with different densities and their photoelectric properties," (in English), Nanoscale Research Letters, Article vol. 7, p. 7, May 2012, Art. no. 246.
[22] Y. M. Chang et al., "Field Emission Properties of Gold Nanoparticle-Decorated ZnO Nanopillars," (in English), Acs Applied Materials & Interfaces, Article vol. 4, no. 12, pp. 6675-6681, Dec 2012.
[23] G. Jimenez-Cadena, E. Comini, M. Ferroni, A. Vomiero, and G. Sberveglieri, "Synthesis of different ZnO nanostructures by modified PVD process and potential use for 1dye-sensitized solar cells," (in English), Materials Chemistry and Physics, Article vol. 124, no. 1, pp. 694-698, Nov 2010.
[24] M. Rusu et al., "High-efficient ZnO/PVD-CdS/Cu(In,Ga)Se-2 thin film solar cells: Formation of the buffer-absorber interface and transport properties," in Thin-Film Compound Semiconductor Photovoltaics, vol. 865, W. Shafarman, T. Gessert, S. Niki, and S. Siebentritt, Eds. (Materials Research Society Symposium Proceedings, Warrendale: Materials Research Society, 2005, pp. 449-455.
[25] M. Tzolov et al., "Vibrational properties and structure of undoped and Al-doped ZnO films deposited by RF magnetron sputtering," (in English), Thin Solid Films, Article vol. 379, no. 1-2, pp. 28-36, Dec 2000.
[26] M. Purica, E. Budianu, E. Rusu, M. Danila, and R. Gavrila, "Optical and structural investigation of ZnO thin films prepared by chemical vapor deposition (CVD)," (in English), Thin Solid Films, Article; Proceedings Paper vol. 403, pp. 485-488, Feb 2002, Art. no. Pii s0040-6090(01)01544-9.
[27] K. Komatsu, Y. Seno, T. Komiyama, Y. Chonan, H. Yamaguchi, and T. Aoyama, "Characteristics of ZnO/CuO heterojunctions formed by direct bonding and PLD with bias voltage application," in Physica Status Solidi C: Current Topics in Solid State Physics, Vol 10, No 10, vol. 10, S. Hildebrandt et al., Eds. (Physica Status Solidi C-Current Topics in Solid State Physics, no. 10) Weinheim: Wiley-V C H Verlag Gmbh, 2013, pp. 1280-1283.
[28] Z. Y. Wang, L. Z. Hu, J. Zhao, J. Sun, and Z. J. Wang, "Effect of the variation of temperature on the structural and optical properties of ZnO thin films prepared on Si (111) substrates using PLD," (in English), Vacuum, Article vol. 78, no. 1, pp. 53-57, Apr 2005.
[29] D. Hu, Y. J. Liu, H. S. Li, X. Y. Cai, X. L. Yan, and Y. D. Wang, "Effect of nickel doping on structural, morphological and optical properties of sol-gel spin coated ZnO films," (in English), Materials Technology, Article vol. 27, no. 3, pp. 243-250, Jul 2012.
[30] A. M. Ali, A. A. Ismail, H. Bouzid, and F. A. Harraz, "Sol-gel synthesis of ZnO-SiO2 thin films: impact of ZnO contents on its photonic efficiency," (in English), Journal of Sol-Gel Science and Technology, Article vol. 71, no. 2, pp. 224-233, Aug 2014.
[31] P. Hazra, S. K. Singh, and S. Jit, "Ultraviolet Photodetection Properties of ZnO/Si Heterojunction Diodes Fabricated by ALD Technique Without Using a Buffer Layer," (in English), Journal of Semiconductor Technology and Science, Article vol. 14, no. 1, pp. 117-123, Feb 2014.
[32] R. Hussin, K. L. Choy, and X. H. Hou, "Fabrication of Multilayer ZnO/TiO2/ZnO Thin Films with Enhancement of Optical Properties by Atomic Layer Deposition (ALD)," in 4th Mechanical and Manufacturing Engineering, Pts 1 and 2, vol. 465-466, A. E. Ismail et al., Eds. (Applied Mechanics and Materials, Durnten-Zurich: Trans Tech Publications Ltd, 2014, pp. 916-+.
[33] C. M. Lee, K. B. Yim, Y. J. Cho, and J. G. Lee, "A comparison of transmittance properties between ZnO : Al films for transparent conductors for solar cells deposited by sputtering of AZO and cosputtering of AZO/ZnO," (in English), Rare Metals, Article; Proceedings Paper vol. 25, pp. 105-109, Oct 2006.
[34] T. H. Kim, Y. G. Ju, L. S. Park, S. H. Lee, J. H. Baek, and Y. M. Yu, "Enhanced Optical Output Power of Tunnel Junction GaN-Based Light Emitting Diodes with Transparent Conducting Al and Ga-Codoped ZnO Thin Films," (in English), Japanese Journal of Applied Physics, Article vol. 49, no. 9, p. 4, 2010, Art. no. 091002.
[35] J. A. Jeong, Y. S. Park, and H. K. Kim, "Comparison of electrical, optical, structural, and interface properties of IZO-Ag-IZO and IZO-Au-IZO multilayer electrodes for organic photovoltaics," (in English), Journal of Applied Physics, Article vol. 107, no. 2, p. 8, Jan 2010, Art. no. 023111.
[36] Y. C. Lin, T. Y. Chen, L. C. Wang, and S. Y. Lien, "Comparison of AZO, GZO, and AGZO Thin Films TCOs Applied for a-Si Solar Cells," (in English), Journal of the Electrochemical Society, Article vol. 159, no. 6, pp. H599-H604, 2012.
[37] T. L. Yang et al., "Structural, optical and electrical properties of AZO/Cu/AZO tri-layer films prepared by radio frequency magnetron sputtering and ion-beam sputtering," (in English), Vacuum, Review vol. 83, no. 2, pp. 257-260, Sep 2008.
[38] P. Banerjee, W. J. Lee, K. R. Bae, S. B. Lee, and G. W. Rubloff, "Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films," (in English), Journal of Applied Physics, Article vol. 108, no. 4, p. 7, Aug 2010, Art. no. 043504.
[39] Z. X. Zhang, Y. X. Guo, X. J. Wang, D. Li, F. L. Wang, and S. S. Xie, "Direct Growth of Nanocrystalline Graphene/Graphite Transparent Electrodes on Si/SiO2 for Metal-Free Schottky Junction Photodetectors," (in English), Advanced Functional Materials, Article vol. 24, no. 6, pp. 835-840, Feb 2014.
[40] W. L. Ma et al., "Photovoltaic Performance of Ultrasmall PbSe Quantum Dots," (in English), Acs Nano, Article vol. 5, no. 10, pp. 8140-8147, Oct 2011.
[41] H. Liu et al., "Fast and Enhanced Broadband Photoresponse of a ZnO Nanowire Array/Reduced Graphene Oxide Film Hybrid Photodetector from the Visible to the Near-Infrared Range," (in English), Acs Applied Materials & Interfaces, Article vol. 7, no. 12, pp. 6645-6651, Apr 2015.