title: The effects of electric field and gate bias pulse on the migration and stability of ionized oxygen vacancies in amorphous In-Ga-Zn-O thin film transistors.
abstract: Oxygen vacancies have been considered as the origin of threshold voltage instability under negative bias illumination stress in amorphous oxide thin film transistors. Here we report the results of first-principles molecular dynamics simulations for the drift motion of oxygen vacancies. We show that oxygen vacancies, which are initially ionized by trapping photoexcited hole carriers, can easily migrate under an external electric field. Thus, accumulated hole traps near the channel/dielectric interface cause negative shift of the threshold voltage, supporting the oxygen vacancy model. In addition, we find that ionized oxygen vacancies easily recover their neutral defect configurations by capturing electrons when the Fermi level increases. Our results are in good agreement with the experimental observation that applying a positive gate bias pulse of short duration eliminates hole traps and thus leads to the recovery of device stability from persistent photoconductivity.
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Oh
authors.affiliation: CAE Team, Memory Division, Samsung Electronics Co. Ltd, Hwaseong 445-701, Korea.
authors.forename: Hyeon-Kyun
authors.initials: HK
authors.lastname: Noh
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: Kee Joo
authors.initials: KJ
authors.lastname: Chang
keywords: amorphous In-Ga-Zn-O; density functional theory; oxide thinfilm transistor; oxygen vacancy