Nowadays thin-film-transistor (TFT) has been widely used in flat panel displays, which is used whether in mobile phone, MP3 or LCD-TV. As the evolution with technology, flat panel display becomes larger and more sophisticated. In the development of large scale display, we need to consider the uniformity of TFT materials. In high-frequency operation (ex. 3-D screen), we have to use the material with higher mobility.

The most commonly used materials in TFT are poly-silicon and amorphous-silicon. Compared the poly-Si and a-Si with a-IGZO, the a-IGZO is considered to be the next generation of materials used in TFTs, due to the perfect uniformity and well mobility at same time. However a-IGZO TFT has several instabilities such as gate bias stress, light
illumination and oxygen adsorption effect.

Previous studies have discussed the phenomenon. However, the instabilities compared in different ambience are rarely mentioned. Now we investigate on the environment-dependent bias stress and photosensitive characteristics of a-IGZO TFT. We use Positive/Negative Bias Stress (PBS/NBS) and light-illumination in different ambience to discuss the degradation of a-IGZO TFT. We found the positive bias stress (PBS) induce the oxygen adsorption on a-IGZO surface by the increasing electron concentration. Besides, the negative bias stress didn’t not cause any degradation on a-IGZO in any kind of environment by channel carrier depletion. Although oxygen will cause the higher threshold voltage, oxygen can effectively suppress the negative threshold voltage shift caused
by photo-generated charges.

[1.1] Y. Kuo, Thin film transistors: materials and processes
(Kluwer Academic, New York, 2004)
[1.2] T. Sameshima, J. Non-Cryst. Solids 227–230, 1196 9(998).
[1.3] Kenji Nomura, Hiromichi Ohta, Akihro Takagi, Thoshio Kamiya, Mashiro Hirano, and Hideo Hosono, Nature (London )432, 488
(2004).
[1.4] Elivra M. C. Fortunato, Pedro M. C. Barquinha, Ana C. M. B. G.Pimentel, Alexandra M. F. Goncalves, Antonia J. S. Marques, Luis M. N.Pereira, and Rodrigo F. P. Martins, Adv.
Mater. Weinheim, Ger. 17, 590 (2005) .
[1.5] R. L. Hoffman, B. H. Norris, and J. F. Wager, Appl. Phys. Lett.
82, 733(2003).
[1.6] C.W. Ow-Yang, D. Spinner, Y. Shigesato, D. Paine, J. Appl.
Phys. 83(1998) 145.
[1.7] H.E.A. Huitema, G.H. Gelinck, J.B.P.H. van der Putten, K.E. Kuijk, C.M. Hart, E. Cantatore, P.T. Herwig, A.J.J.M. van Breemen, D.M. de Leeuw, Nature 424 (2001) 599.
[1.8] G. Thomas, Nature 389 (1997) 907.
[1.9] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, Nature (London) 432, 488 (2004)
[1.10] H. Yabuta, M. Sano, K. Abe, T. Aiba, T. Den, H. Kumomi, K. Nomura, T. Kamiya, and H. Hosono, Appl. Phys. Lett. 89,
112123 (2006)
[1.11] J. K. Jeong, J. H. Jeong, J. H. Choi, J. S. Im, S. H. Kim, H. W. Yang, K.N. Kang, K. S. Kim, T. K. Ahn, H.-J. Chung, M. Kim, B. S. Gu, J.-S. Park,Y.-G. Mo, H. D. Kim, and H. K. Chung, SID Int. Symp. Digest Tech. Papers 39, 1 (2008).
[1.12] M. Ito, C. Miyazaki, N. Ikeda, Y. Kokubo, M. Ishizaki, and Y. Ugajin, Proceedings of the 16th International Workshop on Active-Matrix Flat-panel Displays and Devices (AM-FPD ’09) (The Japan Society of Applied Physics, Tokyo, Japan, 2009),
p. 73.
[1.13] H. Hosono et al., J. Non-Crystalline Solids 203, 334 (1996)
[1.14] Toshio Kamiya1,2 and Hideo Hosono1,2,3* Tokyo Institute of Technology, Japan NPG Asia Mater. 2(1) 15–22 (2010) doi:
10.1038/asiamat.2010.5
[1.15] A. Suresh and J. F. Muth Appl. Phys. Lett.92, 033502 (2008)
[1.16] Te-Chih Chen , Ting-Chang Chang , Tien-Yu Hsieh , Chih-Tsung Tsai , Shih-Ching Chen , Chia-Sheng Lin , Ming-Chin Hung, Chun-Hao Tu, Jiun-Jye Chang, and Po-Lun
Chen , Appl. Phys. Lett. 97, 192103 (2010)
[1.17] Jianke Yao , Ningsheng Xu , Shaozhi Deng , Jun Chen , Juncong She , Han-Ping David Shieh , Fellow , IEEE , Po-Tsun Liu, Senior Member, IEEE, and Yi-Pai Huang IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58,
NO. 4, APRIL 2011

[1.18] Donghun Kang, Hyuck Lim, Changjung Kim, Ihun Song, Jaechoel Park, and Youngsoo Park, Appl. Phys. Lett. 90,
192101 (2007)
[1.19] A. Suresh and J. F. Muth , Appl. Phys. Lett. 92, 033502 (2008)

[3.1] Jae Kyeong Jeong, Hui Won Yang, Jong Han Jeong, Yeon-Gon Mo, and Hye Dong Kim, Appl. Phys. Lett. 93, 123508 (2008)
[3.2] D. Kang, H. Lim, C. Kim, I. Song, J. Park, and Y. Park, Appl. Phys. Lett. 90, 192101 (2007).