本論文為利用原子層沉積法成長高品質超薄(~100 nm)摻鋁氧化鋅薄膜於n型矽基板上來建構一高效率光偵測器之研究。主要為探討不同鋁摻雜濃度對於鋁氧化鋅薄膜之功函數(Work Function)、阻值、結晶性之變化。並以此為出發點探討摻鋁氧化鋅薄膜於n型矽基板上所形成之類蕭特基異質接面能障(Barrier Height of Schottky Hetro-junction)對光電轉換效率或是光響應之關聯性。經XRD實驗分析結果得知，藉由原子層沉積法所成長出摻鋁氧化鋅薄膜為C軸擇優取向；由紫外光-可見光反射光譜分析得知改變摻鋁比例量與光學反射光譜上並未有太大差別，更進一步發現摻鋁氧化鋅薄膜本身為抗反射層且與其它製程結果於薄膜厚度100 nm比較起來電阻率較低。所製作出來之摻鋁氧化鋅與n-type Silicon元件成功證實兩者之間擁有蕭特基接面，並由光學測量與模擬證實其於不同厚度下可以對應不同光學之吸收位置。當摻鋁氧化鋅薄膜厚度約100 nm時，其載子能度可以高達1020/cm2、電阻率可以達到約10-4 Ω/cm等級；經由鹵素燈照光後，光偵測器可於零偏壓下達到短路光電流(Short Circuit Photo Current, Isc)則有4個數量級的提升(亦即光電流/暗電流之比值可高達~10000)，成功證實了高品質摻鋁氧化鋅應用於光偵測器之可行性。

In this work, the strategy of Al-doped ZnO thin film (~100 nm) deposited on n-type silicon in atomic layer deposition (ALD) for high efficiency photodetector is provided and demonstrated successfully. Investigating the correlations between different amount of Al-doped within ZnO and material properties like the work function, resistivity, and crystallinity benefits to create the lower barrier height of Schottky hetero-junction among the interface of Al-doped ZnO thin film and n-type silicon. This Schottky hetro-junction plays an critial role for light detection. Lower barrier height of Schottky hetero-junction introduces the higher both dark current and photocurrent impacting the ratio of photocurrent to dark current typically. According to the verification results from XRD or UV-Visible spectrum of different amount of Al-doped within ZnO, the highly prefer C-axis and insignificant diversity in optical reflection behavior, respectively, provide the evidences for high quality Al-doped ZnO thin film with similar optical reflection. The Al-doped ZnO thin film possesses the extra capabilities of optical antireflection itself and lower resistivity compared with previously studies in this field. Besides, by the electrical or optical verification, the desired low barrier height (~0.35 eV) Schottky hetero-junction among the interface of Al-doped ZnO thin film and n-type silicon or the variant film thickness for modurated absorption spectrum can also be confirmed in this work. In our sample, as the film thickness of 100 nm, the carrier concentration and resistivity is about 1020/cm2 and 10-4 Ω/cm, respectively. Under the halogen illumination, our photodetector without external bias reveals the ratio of photo short current to dark current about 10000 implying feasibility and invention of the device design concept in photodetection application further. 

[1] M. Gratzel, "Photoelectrochemical cells," Nature, vol. 414, pp. 338-344, Nov. 2001.
[2] Y. M. Chi, H. L. Chen, Y. S. Lai, H. M. Chang, Y. C. Liao, C. C. Cheng, et al., "Optimizing surface plasmon resonance effects on finger electrodes to enhance the efficiency of silicon-based solar cells" Energy & Environmental Science, vol. 6, pp. 935-942, Mar 2013.
[3] R. K. Shukla, A. Srivastava, A. Srivastava, and K. C. Dubey, "Growth of transparent conducting nanocrystalline Al doped ZnO thin films by pulsed laser deposition," Journal of Crystal Growth, vol. 294, pp. 427-431, Sep. 2006.
[4] H. Arito, "Risk assessment of hazardous substances revisited," Industrial Health, vol. 53, pp. 193-195, May 2015.
[5] S. J. Jiao, Z. Z. Zhang, Y. M. Lu, D. Z. Shen, B. Yao, J. Y. Zhang, et al., "ZnO P-N junction light-emitting diodes fabricated on sapphire substrates," Applied Physics Letters, vol. 88, Jan. 2006.
[6] 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., ed, 1999, pp. 725-730.
[7] 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," Acs Applied Materials & Interfaces, vol. 4, pp. 1411-1416, Mar 2012.
[8] 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," Nano Energy, vol. 14, pp. 312-339, May 2015.
[9] R. K. Gupta and F. Yakuphanoglu, "Photoconductive Schottky diode based on Al/p-Si/SnS2/Ag for optical sensor applications," Solar Energy, vol. 86, pp. 1539-1545, May 2012.
[10] J. Schalwig, G. Muller, U. Karrer, M. Eickhoff, O. Ambacher, M. Stutzmann, et al., "Hydrogen response mechanism of Pt-GaN Schottky diodes," Applied Physics Letters, vol. 80, pp. 1222-1224, Feb 2002.
[11] P. H. Yeh, Z. Li, and Z. L. Wang, "Schottky-Gated Probe-Free ZnO Nanowire Biosensor," Advanced Materials, vol. 21, pp. 4975-+, Dec 2009.
[12] C. G. Granqvist and A. Hultaker, "Transparent and conducting ITO films: new developments and applications," Thin Solid Films, vol. 411, pp. 1-5, May 2002.
[13] E. Ahilea and A. A. Hirsch, "RESISTANCE OF THIN METAL FILMS GROWN UNDER A LONGITUDINAL ELECTRIC FIELD," Journal of Applied Physics, vol. 42, pp. 5601-&, 1971.
[14] S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, and T. Steiner, "Recent progress in processing and properties of ZnO," Superlattices and Microstructures, vol. 34, pp. 3-32, Jul.-Aug. 2003.
[15] M. Ichimura and Y. Maeda, "Heterojunctions based on photochemically deposited CuxZnyS and electrochemically deposited ZnO," Solid-State Electronics, vol. 107, pp. 8-10, May 2015.
[16] Z. N. Wang, R. M. Yu, X. N. Wen, Y. Liu, C. F. Pan, W. Z. Wu, et al., "Optimizing Performance of Silicon-Based P-N junction Photodetectors by the Piezo-Phototronic Effect," Acs Nano, vol. 8, pp. 12866-12873, Dec. 2014.
[17] P. L. Chen, R. S. Muller, R. D. Jolly, G. L. Halac, R. M. White, A. P. Andrews, et al., "INTEGRATED SILICON MICROBEAM PI-FET ACCELEROMETER," Ieee Transactions on Electron Devices, vol. 29, pp. 27-33, 1982.
[18] M. L. Yin and S. Z. Liu, "One-pot synthesis of Co-doped ZnO hierarchical aggregate and its high gas sensor performance," Materials Chemistry and Physics, vol. 149, pp. 344-349, Jan. 2015.
[19] N. D. Khoang, H. S. Hong, D. D. Trung, N. Van Duy, N. D. Hoa, D. D. Thinh, et al., "On-chip growth of wafer-scale planar-type ZnO nanorod sensors for effective detection of CO gas," Sensors and Actuators B-Chemical, vol. 181, pp. 529-536, May 2013.
[20] 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," Applied Surface Science, vol. 353, pp. 1061-1069, Oct. 2015.
[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," Nanoscale Research Letters, vol. 7, May 2012.
[22] Y. M. Chang, M. L. Lin, T. Y. Lai, H. Y. Lee, C. M. Lin, Y. C. S. Wu, et al., "Field Emission Properties of Gold Nanoparticle-Decorated ZnO Nanopillars," Acs Applied Materials & Interfaces, vol. 4, pp. 6675-6681, Dec. 2012.
[23] 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., ed, 2010, pp. 986-989.
[24] M. Ahmad, H. Y. Sun, and J. Zhu, "Enhanced Photoluminescence and Field-Emission Behavior of Vertically Well Aligned Arrays of In-Doped ZnO Nanowires," Acs Applied Materials & Interfaces, vol. 3, pp. 1299-1305, Apr. 2011.
[25] 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," Applied Surface Science, vol. 264, pp. 162-170, Jan. 2013.
[26] J. G. Lu, T. Kawaharamura, H. Nishinaka, Y. Kamada, T. Ohshima, and S. Fujita, "ZnO-based thin films synthesized by atmospheric pressure mist chemical vapor deposition," Journal of Crystal Growth, vol. 299, pp. 1-10, Feb. 2007.
[27] V. K. Kaushik, T. Ganguli, R. Kumar, C. Mukherjee, and P. K. Sen, "Growth and characterization of ZnO and MgxZn1-xO thin films by aerosol assisted chemical vapor deposition technique," Thin Solid Films, vol. 520, pp. 3505-3509, Feb. 2012.
[28] M. Rusu, T. Glatzel, C. A. Kaufmann, A. Neisser, S. Siebentritt, S. Sadewasser, 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., ed, 2005, pp. 449-455.
[29] 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," Materials Chemistry and Physics, vol. 124, pp. 694-698, Nov. 2010.
[30] 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, M. Cavalleri, L. Herrmann, H. Hopcke, I. Juschak, C. N. DaSilva, et al., Eds., ed, 2013, pp. 1280-1283.
[31] 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," Vacuum, vol. 78, pp. 53-57, Apr. 2005.
[32] 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," Materials Technology, vol. 27, pp. 243-250, Jul. 2012.
[33] 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," Journal of Sol-Gel Science and Technology, vol. 71, pp. 224-233, Aug 2014.
[34] 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," Journal of Semiconductor Technology and Science, vol. 14, pp. 117-123, Feb 2014.
[35] 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, N. H. M. Nor, M. F. M. Ali, R. Ahmad, I. Masood, A. L. M. Tobi, et al., Eds., ed, 2014, pp. 916-921.
[36] 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," Rare Metals, vol. 25, pp. 105-109, Oct. 2006.
[37] 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," Japanese Journal of Applied Physics, vol. 49, 2010.
[38] 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," Journal of Applied Physics, vol. 107, Jan. 2010.
[39] 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," Journal of the Electrochemical Society, vol. 159, pp. H599-H604, 2012.
[40] T. L. Yang, Z. S. Zhang, S. M. Song, Y. H. Li, M. S. Lv, Z. C. Wu, et al., "Structural, optical and electrical properties of AZO/Cu/AZO tri-layer films prepared by radio frequency magnetron sputtering and ion-beam sputtering," Vacuum, vol. 83, pp. 257-260, Sep. 2008.