Analysis of bias stress instability in amorphous InGaZnO thin-film transistors

Edward Namkyu Cho, Jung Han Kang, Chang Eun Kim, Pyung Moon, Ilgu Yun

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108 Citations (Scopus)


In this paper, we report an analysis of electrical bias stress instability in amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Understanding the variations of TFT characteristics under an electrical bias stress is important for commercial goals. In this experiment, the positive gate bias is initially applied to the tested a-IGZO TFTs, and subsequently, the negative gate bias is applied to the TFTs. For comparison with the subsequently negative-gate-bias- applied TFTs, another experiment is performed by directly applying the negative gate bias to the tested TFTs. For the positive gate bias stress, a positive shift in the threshold voltage with no apparent change in the subthreshold swing is observed. On the other hand, when the negative gate bias is subsequently applied, the TFTs exhibit higher mobility with no significant change in, whereas the shift of the is much smaller than that in the positive gate bias stress case. These phenomena are most likely induced by positively charged donor-like subgap density of states and the detrapping of trapped interface charge during the positive gate bias stress. The proposed mechanism was verified by device simulation. Thus, the proposed model can explain the instability for both positive and negative bias stresses in a-IGZO TFTs.

Original languageEnglish
Article number5657252
Pages (from-to)112-117
Number of pages6
JournalIEEE Transactions on Device and Materials Reliability
Issue number1
Publication statusPublished - 2011 Mar

Bibliographical note

Funding Information:
Manuscript received August 31, 2010; revised October 19, 2010 and November 24, 2010; accepted November 24, 2010. Date of publication December 3, 2010; date of current version March 9, 2011. This work was supported by Samsung Electronics as a research project. The authors are with the School of Electrical and Electronic Engineering, Yonsei University, Seoul 120749, Korea (e-mail: Color versions of one or more of the figures in this paper are available online at Digital Object Identifier 10.1109/TDMR.2010.2096508

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Safety, Risk, Reliability and Quality
  • Electrical and Electronic Engineering


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