In this paper, we investigated an anomalous hump in the bottom gate staggered amorphous indium-gallium zinc oxide thin-film transistors. During the positive gate bias stress, a positive threshold voltage shift is observed in transfer curve and an anomalous hump occurs as the stress time increases. The hump becomes more serious as the gate bias stress increases while it is not observed under the negative bias stress. From the simulation of a long range migration of zinc interstitial ions (Zni) and the measurement of the diode characteristics after the constant positive bias stress, the origin of the hump can be explained by the migration of the positively charged mobile Zni during the constant positive gate bias stress, which can be conformed by increasing the concentration of Zni from the result of the Auger ZnL3M4.5M4.5 spectra.

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In this paper, we investigated the anomalous hump in the bottom gate staggered a-IGZO TFTs. During the positive bias stress, a positive threshold voltage shift was observed in the transfer curve and an anomalous hump occurred as the stress time increased. The hump became more serious in higher gate bias stress while it was not observed under the negative bias stress. The analysis of constant gate bias stress indicated that the anomalous hump was influenced by the migration of positively charged mobile interstitial zinc ion towards the top side of the a-IGZO channel layer.

We fabricated pentacene-based organic thin film transistors (OTFTs) with formulated poly[4-vinylphenol] (PVP) gate dielectrics. The solution of gate dielectrics is prepared by adding methylated poly[melamine-co-formaldehyde] (MMF) and photo-initiator (PI) [1-phenyl-2-hydroxy-2-methylpropane-1-one, Darocur1173@Ciba] to PVP By using a small amount (2.4 wt%) of PI, the cross-linking temperature is lowered to 90 degrees C, which is lower than general thermal curing reaction temperature for the cross-linked PVP (> 180 degrees C). The hysteresis and the leakage current of the OTFTs are also decreased by adding the MMF and PI in the PVP gate dielectric.

In this study, we fabricated dual-gate zinc oxide thin film transistors (ZnO TFTs) without additional processes and analyzed their stability characteristics under a negative gate bias stress (NBS) by comparison with conventional bottom-gate structures. The dual-gate device shows superior electrical parameters, such as subthreshold swing (SS) and on/off current ratio. NBS of V GS = −20 V with V DS = 0 was applied, resulting in a negative threshold voltage (V th) shift. After applying stress for 1000 s, the V th shift is 0.60 V in a dual-gate ZnO TFT, while the V th shift is 2.52 V in a bottom-gate ZnO TFT. The stress immunity of the dual-gate device is caused by the change in field distribution in the ZnO channel by adding another gate as the technology computer aided design (TCAD) simulation shows. Additionally, in flicker noise analysis, a lower noise level with a different mechanism is observed in the dual-gate structure. This can be explained by the top side of the ZnO film having a larger crystal and fewer grain boundaries than the bottom side, which is revealed by the enhanced SS and XRD results. Therefore, the improved stability of the dual-gate ZnO TFT is greatly related to the E-field cancellation effect and crystal quality of the ZnO film.

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage (V TH ) under illumination with/without the gate bias, and the amount of shift in V TH is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in V TH under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.