Variation in the threshold voltage of amorphous-In2Ga2ZnO7 thin-film transistors by ultrathin Al2O3 passivation layer

Title
Variation in the threshold voltage of amorphous-In2Ga2ZnO7 thin-film transistors by ultrathin Al2O3 passivation layer
Authors
라상호김언기정지심황은석이승준전우진유연우최정혜황철성
Issue Date
2013-11
Publisher
Journal of Vacuum Science and Technology B
Citation
VOL 31, NO 6, 061205-1-061205-6
Abstract
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.
URI
http://pubs.kist.re.kr/handle/201004/46157
ISSN
10711023
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