1. Hydrogen behavior under X-ray irradiation for a-IGZO thin film transistors.
- Author
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Kim, Dong-Gyu, Lee, Tae-Kwon, Park, Kwon-Shik, Chang, Youn-Gyoung, Han, Kyong-Joo, and Choi, Duck-Kyun
- Subjects
THIN film transistors ,X-rays ,BUFFER layers ,THERMAL desorption ,THRESHOLD voltage ,RADIOGRAPHIC films ,IRRADIATION - Abstract
We studied hydrogen (H) behavior in amorphous In-Ga-Zn-O (a-IGZO) films under X-ray irradiation by evaluating the threshold voltage (V
TH ) shift in a-IGZO thin film transistors (TFTs) with different H concentrations in the active layers. We fabricated three types of a-IGZO TFTs: (i) one without a buffer layer and postannealed in N2 , (ii) one with a H-resolved buffer layer and postannealed in N2 , and (iii) one with a H-resolved buffer layer and postannealed in a mixture of N2 and H2 . All three TFTs showed a negative VTH shift after 100 Gy of X-ray exposure. The degree of VTH shift correlated with an increase in conductivity, which, in turn, corresponds to the H concentration in the active layer of the as-fabricated TFTs. Based on spectroscopic ellipsometry analysis, we confirmed a large increase in the donorlike H related D1 state after X-ray irradiation in high-H concentration a-IGZO films. In addition, an increase in the number of H2 molecules in a-IGZO films after X-ray irradiation was observed via thermal desorption spectroscopy analysis. Therefore, we conclude that the increase in conductivity and/or the resulting negative VTH shift in a-IGZO TFTs during X-ray irradiation can be attributed not only to the state transition from acceptorlike to donorlike H in the as-prepared a-IGZO but also to the incorporation of additional H radicals generated by X-ray irradiation. [ABSTRACT FROM AUTHOR]- Published
- 2020
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