JSTS:Journal of Semiconductor Technology and Science

The Institute of Electronics and Information Engineers (대한전자공학회)
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Comparative Analysis on Positive Bias Stress-Induced Instability under High VGS/Low VDS and Low VGS/High VDS in Amorphous InGaZnO Thin-Film Transistors

  • Kang, Hara (School of Electronic Engineering, Kookmin University) ;
  • Jang, Jun Tae (School of Electronic Engineering, Kookmin University) ;
  • Kim, Jonghwa (School of Electronic Engineering, Kookmin University) ;
  • Choi, Sung-Jin (School of Electronic Engineering, Kookmin University) ;
  • Kim, Dong Myong (School of Electronic Engineering, Kookmin University) ;
  • Kim, Dae Hwan (School of Electronic Engineering, Kookmin University)
  • Received : 2015.04.20
  • Accepted : 2015.08.27
  • Published : 2015.10.30
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Abstract

Positive bias stress-induced instability in amorphous indium-gallium-zinc-oxide (a-IGZO) bottom-gate thin-film transistors (TFTs) was investigated under high $V_{GS}$/low $V_{DS}$ and low $V_{GS}$/high $V_{DS}$ stress conditions through incorporating a forward/reverse $V_{GS}$ sweep and a low/high $V_{DS}$ read-out conditions. Our results showed that the electron trapping into the gate insulator dominantly occurs when high $V_{GS}$/low $V_{DS}$ stress is applied. On the other hand, when low $V_{GS}$/high $V_{DS}$ stress is applied, it was found that holes are uniformly trapped into the etch stopper and electrons are locally trapped into the gate insulator simultaneously. During a recovery after the high $V_{GS}$/low $V_{DS}$ stress, the trapped electrons were detrapped from the gate insulator. In the case of recovery after the low $V_{GS}$/high $V_{DS}$ stress, it was observed that the electrons in the gate insulator diffuse to a direction toward the source electrode and the holes were detrapped to out of the etch stopper. Also, we found that the potential profile in the a-IGZO bottom-gate TFT becomes complicatedly modulated during the positive $V_{GS}/V_{DS}$ stress and the recovery causing various threshold voltages and subthreshold swings under various read-out conditions, and this modulation needs to be fully considered in the design of oxide TFT-based active matrix organic light emitting diode display backplane.

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References

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