Abstract
Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator-semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm2/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 105, and a subthreshold slope of 0.10 V/dec.
Highlights
Dielectric with ZrO2 and Al2O3 (ZAO) dielectric were characterized thoroughly by analytical methods
A weight loss of more than 50% was observed at 150 °C, which was attributed to the solvent evaporation, such as 2-methoxyethanol, the decomposition of the organic group-associated metal salts[17], and the hydrolysis of the ZrO2 solution from zircony chloride octahydrate to zirconyl hydroxylchloride[18]
TFTs based on the ZAO gate dielectric showed a much lower operating voltage of approximately 5 V, which was attributed to the sol-gel processed high k gate dielectric layer with a low thickness, and better subthreshold slope of 0.1 V/dec compared to a-Si TFT because of the high k value of the dielectric
Summary
Dielectric with ZrO2 and Al2O3 (ZAO) dielectric were characterized thoroughly by analytical methods. The output characteristics with mixed ZAO gate dielectrics, as shown, showed that the IDS in the saturation region decreases slightly with increasing amount of Al in the ZAO dielectric films, VGS, and VDS, indicating that electron flow in the channel region becomes slower due to the increased number of scattering events in the metallic pathway with a higher Al density at the ZTO-ZAO interface, and to the enhancement of the potential strength by VGS in the saturation mode.
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