本文利用射頻濺鍍法沉積氧化鎵鋅錫薄膜，改變不同的實驗條件來研究薄膜特性的變化。在本文中，薄膜的結構、光學、以及元素分析皆會一一討論，並將氧化鎵鋅錫薄膜運用於光檢測器及薄膜電晶體中。
第一部分，對氧化鎵鋅錫薄膜，其材料特性會在本部分研究。氧化鎵鋅錫薄膜的結構是非晶相，且表面相當平整。而在光學分析中發現，薄膜在可見光區的穿透率超過80%，且光能隙範圍約落在4.08到4.23電子伏特間，顯示氧化鎵鋅錫薄膜具有寬能隙及高透明度這兩項特性。在元素分析上，XPS被用來分析薄膜的化學狀態。從元素比例可得到，當通氧量的比率增加時，薄膜內鎵的成分會下降。且在退火溫度為攝氏300度時，薄膜的氧空缺數量會隨著通氧量的增加而降低。
第二部分，則是將上一部份的薄膜實際運用於光檢測器中。調整通氧比率及退火溫度對於薄膜的特性是相當重要的。從結果發現，所有條件製作出的光檢測器，其暗電流皆為10-11 安培等級。在本研究中，最好的實驗條件為樣品B2，其通氧比為百分之4，退火溫度為攝氏300度。其光暗電流比、暗電流、響應度、拒斥比、上升時間、下降時間分別為4.95×104、43皮安培、1.58×10-1 安培/瓦、 5.87×104、 41 秒及 4 秒。
第三部分，氧化鎵鋅錫薄膜會以射頻濺鍍法及共濺鍍法沉積。透過變化通氧比及退火溫度來研究薄膜的變化。量測顯示薄膜是非晶相，表面比第一部分的薄膜稍微粗糙。其在可見光下的穿透率高於百分之80。薄膜的光能隙約為3.71到4.08電子伏特。由氧1s圖譜可知，在退火溫度為攝氏300度時，氧空缺的數量隨通氧比的上升而下降。
第四部份，將氧化鎵鋅錫薄膜運用於薄膜電晶體的主動層。九種實驗條件皆與第三部分相同。通氧比百分之4、退火溫度為攝氏300度的樣品E2有最佳的表現。其臨界電壓、電子遷移率、開關比及次臨界擺幅分別為2.98 V、3.2 cm2/Vs、1.5 ×106及0.392 V/decade。
在照光下氧化鎵鋅錫薄膜電晶體的效能變化也在本文研究中討論。在照光下表現最好的元件為樣品E2，其拒斥比為1.61 ×106。樣品E1有最好的開關特性，其上升時間和下降時間分別為116秒及15秒。因正偏壓應力而造成樣品E2的臨界電壓正移了4.12 V，而負偏壓應力對樣品E3施加造成樣品E3的臨界電壓負移了1.18 V。

In this thesis, gallium zinc tin oxide (GaZTO) thin films are deposited by Radio-Frequency (RF) sputtering system under the various experimental conditions. The structural, optical, and element analysis are conducted on GaZTO thin films. GaZTO thin films are applied to photodetector and thin film transistor (TFTs) in this study.
In the first part, the material characteristics of GaZTO thin films are studied. Structural characteristics of GaZTO thin films are amorphous and smooth on the surface. Transmittance of GaZTO thin films is greater than 80 % in visible light region, and its optical bandgap ranges from 4.08 to 4.23 eV. Therefore, GaZTO thin films are widely bandgap and high transparency. For elemental analysis, XPS is utilized to analyze the chemical state in GaZTO thin films. The elemental ratio demonstrates that the content of gallium decreases when the oxygen flow ratio increases. The amount of oxygen vacancy decreases with increasing oxygen flow ratio when annealing temperature is 300˚C.
In the second part, GaZTO thin films are applied to photodetector. Adjusting oxygen flow ratio and annealing temperature is an important role to the properties of GaZTO thin films. The consequence exhibits that dark current of all samples is at 10-11 A. The optimized condition (Sample B2) in this study is oxygen flows ratio of 4% and annealing temperature of 300 ˚C. Photo/Dark ratio, dark current, responsivity, rejection ratio, rise times, and fall times of sample B2 are 4.95×104, 43 pA, 1.58×10-1 A/W, 5.87×104, 41 s, 4 s, respectively.
In the third part, GaZTO thin films are deposited by RF sputtering system and co-sputtering method. The oxygen flows ratio and annealing temperatures are varied to study the effect on the GaZTO thin films. The measurement reveals GaZTO thin films are amorphous and slightly rough compared with GaZTO thin films deposited by one target. Transmittance of GaZTO thin films is greater than 80 % in visible light region, and its optical bandgap ranges from 3.71 to 4.08 eV. It is noted that the amount of oxygen vacancy decreases with increasing oxygen flow ratio when annealing temperature is 300˚C from O1s spectrum.
In the fourth part, GaZTO thin films are introduced to the active layer in the TFTs with SiO2 oxide layer. Nine experimental conditions are the same as the third part. Sample E2, whose annealing temperature and oxygen flows ratio are 300˚C and 4%, has the optimized performance. Threshold voltage, mobility, on-off ratio, and subthreshold swing of sample E2 are 2.98 V, 3.2 cm2/Vs, 1.5 ×106, and 0.392 V/decade, respectively. Besides, the performance of GaZTO TFT under illumination is also studied. The optimized device under illumination is sample E2, whose rejection ratio is 1.61 ×106. Sample E1 has the best switching characteristics, and its rise times and fall times of sample E1 are 116 s and 15 s, respectively. The shift of Vth of sample E2 in PBS test is 4.12 V, and that of sample E3 in NBS test is -1.18 V.

[1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, H. Hosono, “Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors,” Nature, vol. 432, pp. 488-492, 2004.
[2] J. I. Song, J. S. Park, H. Kim, Y. W. Heo, J. H. Lee, J. J. Kim, “Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature,” Appl. Phys. Lett., vol. 90, 022106, 2007.
[3] Z. Li, L. Xu, A. Abliz, Y. Hua, J. Li, Y. Shi, W. Liu, L. Liao, “Electrical Properties in Group IV Elements-Doped ZnO Thin-Film Transistors,” J. Disp. Technol., vol. 11, pp. 670-673, 2015.
[4] B. Walker, A. K.Pradhan, B. Xiao, “Low temperature fabrication of high performance ZnO thin film transistors with high-k dielectrics,” Solid-State Electron., vol. 111, pp. 58-61, 2015
[5] D. Han, Z. Chen, Y. Y. Cong, W. Yu, X. Zhang, Y. Wang, “High-Performance Flexible Tin-Zinc-Oxide Thin-Film Transistors Fabricated on Plastic Substrates,” IEEE Trans. Electron Dev., vol. 63, pp.3360-3363, 2016.
[6] B. D. Ahn, D. W. Choi, C. H. Choi, J. S. Park, “The effect of the annealing temperature on the transition from conductor to semiconductor behavior in zinc tin oxide deposited atomic layer deposition,” Appl. Phys. Lett., vol. 105, pp. 092103-1-092103-4, 2014.
[7] S. B. Zhang, S.-H. Wei, A. Zunger, “Intrinsic n-type versus p-type doping asymmetry and the defect physics of ZnO,” Phys. Rev. B, vol. 63, pp. 075205-1–075205-7, 2001.
[8] H. Hosono, “Ionic amorphous oxide semiconductors: Material design, carrier transport, and device application,” J. Non-Cryst. Solids, vol. 352, pp. 851-858, 2006.
[9] H. Li, M. Tung, J. Jiao, “TiO2 Nanoparticle and ZnO Nanowire Composite for Solar Cell Application,” Microsc. microanal., vol. 15, pp. 1428-1429, 2009
[10] M. J. Chen, Y. T. Shih, M. K. Wu, H. C. Chen, H. L. Tsai, W. C. Li, J. R. Yang, H. Kuan, M. Shiojiri, “Structure and Ultraviolet Electroluminescence of n-ZnO/SiO2-ZnO Nanocomposite/p-GaN Heterostructure Light-Emitting Diodes,” IEEE Trans. Electron Dev., vol. 57, pp. 2195-2202, 2010.
[11] Y. Lu, I.A. Dajani, R.J. Knize, “ZnO nanorod arrays as p–n heterojunction ultraviolet photodetectors,” Electron. Lett., vol. 42, pp. 1309-1311, 2006.
[12] B. S. Ong, C. S. Li, Y. Li, Y. L. Wu, R. Loutfy, “Stable, Solution-Processed, High-Mobility ZnO Thin-Film Transistors,” J. Am. Chem. Soc., vol. 129, pp. 2750–2751, 2007.
[13] D. R. Evans, M. F. Lewis, E. Patterson, “Sputtered ZnO surface-wave transducers,” Electron. Lett., vol. 7, pp. 557-558, 1971.
[14] J. H. Chung, J. Y. Lee, H. S. Kim, N. W. Jang, J. H. Kim, “Effect of thickness of ZnO active layer on ZnO-TFT's characteristics,” Thin Solid Films, vol. 516, pp. 5597-5601, 2007.
[15] H. H. Quon, D. P. Malanka, “Chemical vapour deposition of epitaxial ZnO films,” Mater. Res. Bull., vol.10, pp. 349-354, 1975.
[16] R. Macaluso, M. Mosca, V. Costanza, A. D’Angelo, G. Lullo, F. Caruso, C. Calì, F. Di Franco, M. Santamaria, F. Di Quarto, “Resistive switching behaviour in ZnO and VO2 memristors grown by pulsed laser deposition,” Electron. Lett., vol. 50, pp. 262-263, 2014.
[17] S. H. K. Park, Y. E. Lee, “Controlling preferred orientation of ZnO thin films by atomic layer deposition,” J. Mater. Sci., vol. 39, pp. 2195-2197, 2004.
[18] F. H. Alshammari, P. K. Nayak, Z. W. Wang, H. N. Alshareef, “Enhanced ZnO Thin-Film Transistor Performance Using Bilayer Gate Dielectrics,” ACS Appl. Mater. Interfaces, vol. 8, pp. 22751-22755, 2016.
[19] S. Hwangbo, Y. J. Lee, K. S. Hwang, “Photoluminescence of ZnO layer on commercial glass substrate prepared by sol–gel process,” Ceram. Int., vol. 34, pp. 1237-1239, 2008.
[20] G. Li, D. Xie, T. T. Feng, J. L. Xu, X. W. Zhang, T. L. Ren, “The influence of channel layer thickness on the electrical properties of ZnO TFTs,” Solid-State Electron., vol. 95, pp. 32-35, 2014.
[21] Y. Ohya, T. Niwa, T. Ban, Y. Takahashi, “Thin Film Transistor of ZnO Fabricated by Chemical Solution Deposition,” Jpn. J. Appl. Phys., vol. 40, pp. 297–298, 2001.
[22] M. Miyazaki, K. Sato, A. Mitsui, H. Nishimura, “Properties of Ga-doped ZnO films,” J. Non-Cryst. Solids, vol. 218, pp. 323-328, 1997.
[23] W. J. Park, H. S. Shin, B. D. Ahn, G. H. Kim, S. M. Lee, K. H. Kim, H. J. Kim, “Investigation on doping dependency of solution-processed Ga-doped ZnO thin film transistor,” Appl. Phys. Lett., vol. 93, pp. 083508-1-083508-3, 2008.
[24] M. Chen, X. Wang, Y. H. Yu, Z. L. Pei, X. D. Bai, C. Sun, R. F. Huang, L. S. Wen, “X-ray photoelectron spectroscopy and auger electron spectroscopy studies of Al-doped ZnO films,” Appl. Surf. Sci., vol. 158, pp. 134-140, 2000.
[25] M. L. Lin, J. M. Huang, C. S. Ku, C. M. Lin, H. Y. Lee, J. Y. Juang, “High mobility transparent conductive Al-doped ZnO thin films by atomic layer deposition,” J. Alloy. Compd., vol. 727, pp. 565-571, 2017.
[26] H. R. Kim, J. Park, S. H. Lee, G. H. Lee, P. G. Song, Y. C. Kang, D. H. Kim, “Effects of Ga Concentration on Electrical and Physical Properties of Amorphous Ga-Zn-Sn-O Semiconductor Thin Films,” Electrochem. Solid State Lett., vol. 14, pp. H411-H414, 2011.
[27] B. D. Ahn, H. J. Jeon, J. S. Park, “Effects of Ga:N Addition on the Electrical Performance of Zinc Tin Oxide Thin Film Transistor by Solution-Processing,” ACS Appl. Mater. Interfaces, vol. 6, pp. 9228-9235, 2014.
[28] Y. Ogo, K. Nomura, H. Yanagi, T. Kamiya, M. Hirano, H. Hosono, “Amorphous Sn–Ga–Zn–O channel thin-film transistors,” Phys. Status Solidi A-Appl. Mat., vol. 205, pp. 1920–1924, 2008.
[29] D. H. Kim, H. R. Kim, J. D. Kwon, G. H. Lee, J. Park, Y. C. Kang, “Effects of post-annealing on electrical properties of amorphous Ga-doped Zn–Sn–O semiconductor films,” J. Non-Cryst. Solids, vol. 358, pp. 2616-2619, 2012.
[30] A. Ortiz, J. C. Alonso, E. Andrade, C. Urbiola, “Structural and Optical Characteristics of Gallium Oxide Thin Films Deposited by Ultrasonic Spray Pyrolysis,” J. Electrochem. Soc., vol. 148, pp. F26-F29, 2001.
[31] Z. M. Jarzebski, J. P. Marton, “Physical Properties of SnO2 Materials III. Optical Properties,” J. Electrochem. Soc., vol. 123, pp. C333-C346, 1976.
[32] Z. M. Jarzebski, J. P. Marton, “Physical Properties of SnO2 Materials I. Preparation and Defect Structure,” J. Electrochem. Soc., vol. 123, pp. C199-C205, 1976.
[33] H. Klauk,” Organic thin-film transistors”, Chem. Soc. Rev., vol. 39, pp. 2643-2666, 2010.
[34] C. M. Hu, “Modern semiconductor devices for integrated circuits”, Pearson Education, Boston, pp. 265, 2010.
[35] Q. J. Jiang, C. J. Wu, L. Feng, L. Gong, Z. Z. Ye, J. G. Lu, “High-response of amorphous ZnSnO sensors for ultraviolet and ethanol detections,” Appl. Surf. Sci., vol. 357, pp. 1536-1540, 2015.
[36] Y. J. Zhang, J. J. Wang, H. F. Zhu, H. Li, L. Jiang, C. Y. Shu, W. P. Hu, C. R. Wang, “High performance ultraviolet photodetectors based on an individual Zn2SnO4 single crystalline nanowire,” J. Mater. Chem., vol. 20, pp. 9858-9860, 2010.
[37] W. H. Wang, X. H. Pan, W. Dai, Y. Y. Zeng, Z. Z. Ye, “Ultrahigh sensitivity in the amorphous ZnSnO UV photodetector,” RSC Adv., vol. 6, pp. 32715-32720, 2016.
[38] L. W. Sang, M. Y. Liao, M. Sumiya, “A Comprehensive Review of Semiconductor Ultraviolet Photodetectors: From Thin Film to One-Dimensional Nanostructures,” Sensors, vol. 13, pp. 10482-10518, 2013.
[39] H. K. Yadav, K. Sreenivas, V. Gupta, “Enhanced response from metal/ZnO bilayer ultraviolet photodetector,” Appl. Phys. Lett., vol. 90, pp. 172113-1-172113-3, 2007
[40] Y. K. Su, S. J. Chang, Y. D. Jhou, S. L. Wu, C. H. Liu, “GaN Metal-Semiconductor-Metal Photodetectors With SiN/GaN Nucleation Layer,” IEEE Sens. J., vol. 8, pp. 1693-1697, 2008.
[41] Y. L. Wu, S. J. Chang, W. Y. Weng, C. H. Liu, T. Y. Tsai, C. L. Hsu, K. C. Chen, “Ga2O3 Nanowire Photodetector Prepared on SiO2/Si Template,” IEEE Sens. J., vol. 13, pp. 2368-2373, 2013.
[42] W. H. Wang, X. H. Pan, W. Dai, Y. Y. Zeng, Z. Z. Ye,“Ultrahigh sensitivity in the amorphous ZnSnO UV photodetector,” RSC Adv., vol. 6, pp. 32715-32720, 2016.
[43] P. Wu, J. Zhang, J. G. Lu, X. F. Li, C. J. Wu, R. J. Sun, L. Feng, Q. J. Jiang, B. Lu, X. H. Pan, Z. Z. Ye, “Instability Induced by Ultraviolet Light in ZnO Thin-Film Transistors,” IEEE Trans. Electron Devices, vol. 61, pp. 1431-1435, 2014.
[44] S. Han, Z. Z. Zhang, J. Y. Zhang, L. K. Wang, J. Zheng, H. F. Zhao, Y. Zhang, M. M. Jiang, S. P. Wang, D. X. Zhao, C. X. Shan, B. H. Li, D. Z. Shen, “Photoconductive gain in solar-blind ultraviolet photodetector based on Mg0.52Zn0.48Othin film,” Appl. Phys. Lett., vol. 99, pp. 242105-1- 242105-4,2011
[45] L.K. Wang, Z.G. Ju, C.X. Shan, J. Zheng, D.Z. Shen, B. Yao, D.X. Zhao, Z.Z. Zhang, B.H. Li, J.Y. Zhang, “MgZnO metal-semiconductor-metal structured solar-blind photodetector with fast response,” Solid State Commun., vol. 149, pp. 2021-2023, 2009.
[46] W. Zhang, D. Y. Jiang, Z. X. Guo, X. J. Yang, N. Hu, Y. H. Duan, S. Gao, Q. C. Liang, T. Zheng, J. W. Lv, “Controlling responsivity depends on change of interdigital electrodes in planar MgZnO UV photodetectors,” Superlattices Microstruct., vol. 115, pp. 177-182, 2018.
[47] C. H. Liu, A. Piyadasa, M. Piech, S. Dardona, Z. Ren, P. X. Gao, “Tunable UV response and high performance of zinc stannate nanoparticle film photodetectors,” J. Mater. Chem. C., vol. 4, pp. 6176-6184, 2016.
[48] S. Singh, “Al doped ZnO based metal-semiconductor-metal and metal-insulator-semiconductor-insulator-metal UV sensors,” Optik, vol. 127, pp. 3523-3526, 2016.
[49] T. Tut, T. Yelboga, E. Ulker, E. Ozbay, “Solar-blind AlGaN-based p-i-n photodetectors with high breakdown voltage and detectivity,” Appl. Phys. Lett., vol. 92, pp. 103502-1-103502-3,2008.
[50] L. C. Liu, J. S. Chen, J. S. Jeng, W. Y. Chen, “Variation of Oxygen Deficiency in Solution-Processed Ultra-Thin Zinc-Tin Oxide Films to Their Transistor Characteristics,” ECS J. Solid State Sci. Technol., vol. 2, pp. Q59-Q64, 2013.
[51] J. S. Park, W. J. Maeng, H. S. Kim, J. S. Park, “Review of recent developments in amorphous oxide semiconductor thin-film transistor devices,” Thin Solid Films, vol. 520, pp. 1679-1693, 2012.
[52] M. J. Yu, R. P. Lin, Y. H. Chang, T. H. Hou, “High-Voltage Amorphous InGaZnO TFT With Al2O3 High-k Dielectric for Low-Temperature Monolithic 3-D Integration,” IEEE Trans. Electron Devices, vol. 63, pp. 3944-3949, 2016.
[53] J. Q. Zhang, Z. X. Li, L. P. Shen, C. Ye, B. Y. Wang, H. Wang, “Characteristics of ZnO thin film transistor using Ta2O5 gate dielectrics,” Thin Solid Films, vol. 544, pp. 281-284, 2013.
[54] T. M. Pan, F. H. Chen, Y. H. Shao, “High-performance InGaZnO thin-film transistor incorporating a HfO2/Er2O3/HfO2 stacked gate dielectric,” RSC Adv., vol. 5, pp. 51286-51289, 2015.
[55] M. W. Ma, C. Y. Chen, W. C. Wu, C. J. Su, K. H. Kao, T. S. Chao, T. F. Lei, “Reliability Mechanisms of LTPS-TFT With HfO2 Gate Dielectric: PBTI, NBTI, and Hot-Carrier Stress,” IEEE Trans. Electron Devices, vol. 55, pp. 1153-1160, 2008.
[56] S. H., S. Lee, M. Mativenga, J. Jang, “Reduction of Negative Bias and Light Instability of a-IGZO TFTs by Dual-Gate Driving,” IEEE Electron Device Lett., vol. 35, pp. 93-95, 2014.
[57] T. C. Chen, T. C. Chang, T. Y. Hsieh, C. T. Tsai, S. C. Chen, C. S. Lin, F. Y. Jian, M. Y. Tsai, “Investigation of the gate-bias induced instability for InGaZnO TFTs under dark and light illumination,” Thin Solid Films, vol. 520, pp. 1422-1426, 2011.
[58] K. Nomura, T. Kamiya, H. Hosono, “Ambipolar Oxide Thin-Film Transistor,” Adv. Mater., vol. 23, pp. 3431-3434, 2011.
[59] T. Lin, X. L. Li, J. Jang, “High performance p-type NiOx thin-film transistor by Sn doping,” Appl. Phys. Lett., vol. 108, pp. 233503-1-233503-6, 2016.
[60] S. Han, A. J. Flewitt, “The Origin of the High Off-State Current in p-Type Cu2O Thin Film Transistors,” IEEE Electron Device Lett., vol. 38, pp. 1394-1397, 2017.