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采用溶液法在玻璃衬底上制备InGaZnO薄膜, 并以InGaZnO为沟道层制备底栅顶接触型薄膜晶体管, 研究了退火温度和Ga含量对InGaZnO薄膜和晶体管电学性能的影响. 研究表明, 退火可以明显改善溶液法制备InGaZnO薄膜晶体管的电学性能. 退火温度的升高会导致薄膜晶体管阈值电压的负向漂移, 并且饱和迁移率和电流开关比增大. X射线光电子能谱测量表明, 随退火温度的增加, InGaZnO薄膜表面吸附氧减少, 沟道层中氧空位增多导致电子浓度增大. 退火温度为380 ℃时, 晶体管获得最佳性能. 饱和迁移率随Ga含量的增加而减小. In:Ga:Zn 摩尔比为5:1.3:2时, 晶体管达到最佳性能: 饱和迁移率为0.43 cm2/(Vs), 阈值电压为1.22 V, 开关电流比为4.7104, 亚阈值摆幅为0.78 V/decade.Oxide thin film transistor with an oxide channel layer is investigated to cater to the requirements of transparent electronics for the high mobility, good uniformity, and large band gap. Owing to its special conduction mechanism, high carrier mobility can be realized even in the amorphous phase. Oxide-based thin films have been prepared by using a number of methods, such as pulsed laser deposition, chemical vapor deposition, radio-frequency sputtering and solution-derived process. Solution processing is commonly used in TFT applications because of its simplicity and potential application in printed device fabrication. In the solution process, the conductivity of multicomponent oxide films can be controlled by incorporating charge-controlling cations. In this paper, bottom-gat topcontact thin film transistors are fabricated by using solution processed InGaZnO channel layers. The effects of annealing temperature and Ga content on the properties of thin film transistor are examined. Optical transmittance of InGaZnO thin film is greater than 80% in the visible region. Electrical characteristics of InGaZnO thin film transistor are improved by increasing annealing temperature. The threshold voltage of solution-processed InGaZnO transistor decreases from 6.74 to -0.62 V with annealing temperature increasing from 250 to 400 ℃, owing to the increase in electron concentration in the active layer. A lower annealing temperature suppresses the generation of carriers outside of the control of Ga cations. X-ray photoelectron spectrum measurement shows that the electron concentration increases because oxygen vacancies generate electrons. The incorporation of Ga into a InZnO compound system results in reducing the carrier concentration of the film and an off-current of thin film transistor. As the Ga ratio is increased at an identical In and Zn content, the carrier concentration of the film decreases and the threshold voltage of thin film transistor shifts towards the positive direction. As the content of Ga is increased in the oxide active layer of transistor, the subthreshold amplitude decreases, and the on/off ratio is improved. This is a consequence of the Ga ions forming strong chemical bonds with oxygen as compared with the Zn and In ions, acting as a carrier suppressor. The performances of thin film transistor with an atomic ratio of In: Ga: Zn=5:1.3:2 are optimized as follows: saturation mobility of 0.43 cm2/(Vs), threshold voltage of -1.22 V, on/off current ratio of 4.7104, subthreshold amplitude of 0.78 V/decade.
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Keywords:
- InGaZnO /
- thin film transistor /
- solution process /
- thermal annealing
[1] Hoffman R L, Norris B J, Wager J F 2003 Appl. Phys. Lett. 82 733
[2] Wager J F 2003 Science 300 1245
[3] Hosono H, Yasukawa M, Kawazoe H 1996 J. Non-Cryst. Solids 203 334
[4] Choi H S, Jeon S, Kim H, Shin J, Kim C, Chung U I 2012 Appl. Phys. Lett. 100 173501
[5] Choi W S 2012 Electron. Mater. Lett. 8 87
[6] Sangwook K, Jae Chul P, Dae Hwan K, Jang-Sik L 2013 Jpn. J. Appl. Phys. 52 041701
[7] Li X F, Xin E L, Shi J F, Chen L L, Li C Y, Zhang J H 2013 Acta Phys. Sin. 62 108503 (in Chinese) [李喜峰, 信恩龙, 石继锋, 陈龙龙, 李春亚, 张建华 2013 物理学报 62 108503]
[8] Lee S Y, Kim D H, Chong E, Jeon Y W, Kim D H 2011 Appl. Phys. Lett. 98 122105
[9] Liu K H, Chang T C, Wu M S, Hung Y S, Hung P H, Hsieh T Y, Chou W C, Chu A K, Sze S M, Yeh B L 2014 Appl. Phys. Lett. 104 133503
[10] Nomura K, Ohta H, Ueda K, Kamiya T, Hirano M, Hosono H 2003 Science 300 1269
[11] Kim G H, Shin H S, Ahn B D, Kim K H, Park W J, Kim H J 2009 J. Electrochem. Soc. 156 H7
[12] Kamiya T, Nomura K, Hosono H 2010 Phys. Status Solidi A 207 1698
[13] Fan J C C, Goodenough J B 1977 J. Appl. Phys. 48 3524
[14] Kumar B, Gong H, Akkipeddi R 2005 J. Appl. Phys. 97 063706
[15] Ahn B D, Shin H S, Kim G H, Park J S, Kim H J 2009 Jpn. J. Appl. Phys. 48 03B019
[16] Takechi K, Nakata M, Eguchi T, Yamaguchi H, Kaneko S 2009 Jpn. J. Appl. Phys. 48 011301
[17] Kim D, Koo C Y, Song K, Jeong Y, Moon J 2009 Appl. Phys. Lett. 95 103501
[18] Choi J H, Hwang S M, Lee C M, Kim J C, Park G C, Joo J, Lim J H 2011 J. Cryst. Growth 326 175
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[1] Hoffman R L, Norris B J, Wager J F 2003 Appl. Phys. Lett. 82 733
[2] Wager J F 2003 Science 300 1245
[3] Hosono H, Yasukawa M, Kawazoe H 1996 J. Non-Cryst. Solids 203 334
[4] Choi H S, Jeon S, Kim H, Shin J, Kim C, Chung U I 2012 Appl. Phys. Lett. 100 173501
[5] Choi W S 2012 Electron. Mater. Lett. 8 87
[6] Sangwook K, Jae Chul P, Dae Hwan K, Jang-Sik L 2013 Jpn. J. Appl. Phys. 52 041701
[7] Li X F, Xin E L, Shi J F, Chen L L, Li C Y, Zhang J H 2013 Acta Phys. Sin. 62 108503 (in Chinese) [李喜峰, 信恩龙, 石继锋, 陈龙龙, 李春亚, 张建华 2013 物理学报 62 108503]
[8] Lee S Y, Kim D H, Chong E, Jeon Y W, Kim D H 2011 Appl. Phys. Lett. 98 122105
[9] Liu K H, Chang T C, Wu M S, Hung Y S, Hung P H, Hsieh T Y, Chou W C, Chu A K, Sze S M, Yeh B L 2014 Appl. Phys. Lett. 104 133503
[10] Nomura K, Ohta H, Ueda K, Kamiya T, Hirano M, Hosono H 2003 Science 300 1269
[11] Kim G H, Shin H S, Ahn B D, Kim K H, Park W J, Kim H J 2009 J. Electrochem. Soc. 156 H7
[12] Kamiya T, Nomura K, Hosono H 2010 Phys. Status Solidi A 207 1698
[13] Fan J C C, Goodenough J B 1977 J. Appl. Phys. 48 3524
[14] Kumar B, Gong H, Akkipeddi R 2005 J. Appl. Phys. 97 063706
[15] Ahn B D, Shin H S, Kim G H, Park J S, Kim H J 2009 Jpn. J. Appl. Phys. 48 03B019
[16] Takechi K, Nakata M, Eguchi T, Yamaguchi H, Kaneko S 2009 Jpn. J. Appl. Phys. 48 011301
[17] Kim D, Koo C Y, Song K, Jeong Y, Moon J 2009 Appl. Phys. Lett. 95 103501
[18] Choi J H, Hwang S M, Lee C M, Kim J C, Park G C, Joo J, Lim J H 2011 J. Cryst. Growth 326 175
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