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

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.