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Passivated Hf–In–Zn–O (HIZO) thin film transistors suffer from a negative threshold voltage shift under visible light stress due to persistent photoconductivity (PPC). Ionization of oxygen vacancy sites is identified as the origin of the PPC following observations of its temperature- and wavelength-dependence. This is further corroborated by the photoluminescence spectrum of the HIZO. We also show that the gate voltage can control the decay of PPC in the dark, giving rise to a memory action.

Threshold voltage dependence on channel length in amorphous-indium-gallium-zinc-oxide thin-film transistors Appl. Phys. Lett. 102, 083508 (2013); 10.1063/1.4793996Low-temperature processed Schottky-gated field-effect transistors based on amorphous gallium-indium-zincoxide thin films Appl. Phys. Lett. 97, 243506 (2010); 10.1063/1.3525932High mobility amorphous zinc oxynitride semiconductor material for thin film transistors Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application J.

The world's largest (15‐inch) XGA active matrix liquid crystal display (AMLCD) panel made with IGZO TFTs (W/L=29.5/4 μm) was fabricated and evaluated with the field effective mobility of 4.2±0.4 cm2/V‐s, Vth of −1.3±1.4V and sub‐threshold swing (SS) of 0.96±0.10 V/dec. for a manufacturing‐oriented process, the main factors affecting threshold voltage (Vth) of the IGZO thin film transistors (TFT) are investigated. On the glass surface, thicker regions of IGZO film have a negative threshold voltage shift. A dry etching process of molybdenum source and drain (S/D) causes negative shift of the average threshold voltage compared to wet etching in the bottom gate back channel etched TFTs. However, optimization of SiOx passivation and subsequent annealing shift average Vth positively and reduce Vth variation.

Electrical bias and light stressing followed by natural recovery of amorphous hafnium-indium-zinc-oxide (HIZO) thin film transistors with a silicon oxide/nitride dielectric stack reveals defect density changes, charge trapping and persistent photoconductivity (PPC). In the absence of light, the polarity of bias stress controls the magnitude and direction of the threshold voltage shift (ΔVT), while under light stress, VT consistently shifts negatively. In all cases, there was no significant change in field-effect mobility. Light stress gives rise to a PPC with wavelength-dependent recovery on time scale of days. We observe that the PPC becomes more pronounced at shorter wavelengths.