Variation in the threshold voltage of amorphous-In2Ga2ZnO7 thin-film transistors by ultrathin Al2O3 passivation layer
- Variation in the threshold voltage of amorphous-In2Ga2ZnO7 thin-film transistors by ultrathin Al2O3 passivation layer
- 라상호; 김언기; 정지심; 황은석; 이승준; 전우진; 유연우; 최정혜; 황철성
- Issue Date
- Journal of Vacuum Science and Technology B
- VOL 31, NO 6, 061205-1-061205-6
- The variations in the performance of amorphous In2Ga2ZnO7 thin-film transistors with ultrathin
Al2O3 passivation layers deposited by atomic layer deposition (ALD) were examined. As the ALD
Al2O3 deposition cycle number increased, the threshold voltage shifted to the negative voltage
direction, while the saturation mobility was invariant. These variations are attributed to the removal
of electronegative species such as OH- groups on back channel surface, while the bulk properties
of the channel were hardly affected during the ALD. The ALD may not influence the oxygen
vacancy concentration in the amorphous In2Ga2ZnO7 channel. The OH- groups on the Al2O3
surface further influenced the threshold voltage through capacitive coupling. The shifted properties recover the initial values after long-term exposure to air (100 days), by diffusion of OH- to the Al2O3/In2Ga2ZnO7 interface. These findings were further confirmed by spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization using a p++-Si/In2Ga2ZnO7 junction diode.
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