Fabrication and Electrical Characterization of ZnO Thin-Film Transistors Using Anodized Aluminum Oxide as Gate Dielectric

Abstract

This study reports the deposition and characterization of zinc oxide thin films and the fabrication of a ZnO thin-film transistor employing anodized aluminium oxide as the gate dielectric. Profilometric analysis revealed a ZnO film thickness of 1,308.14 nm and an AAO dielectric thickness of 15,414.41 nm. The optical properties of the ZnO film were investigated using absorbance, transmittance, reflectance and direct optical band-gap measurements. The film exhibited stronger absorption in the short-wavelength region and increasing optical transmission toward longer wavelengths, indicating the characteristic wide- band-gap optical response of ZnO. The direct optical band gap was determined to be 3.20 eV. Electrical characterization of the fabricated ZnO/AAO TFT demonstrated clear gate-voltage- dependent drain-current modulation, consistent with n-channel ZnO TFT operation. The threshold voltage was approximately 6.20 V, while the maximum drain current reached 2.864 mA. An off-state current of 17.37 μA resulted in an on/off current ratio of approximately 164.84. The maximum transconductance was 3.002 mS, and the subthreshold swing was approximately 206 mV/decade. The extracted field-effect mobility was 4.15 cm2/Vs, indicating measurable charge transport and effective gate modulation in the ZnO channel. The results demonstrate that the ZnO/AAO structure possesses the essential optical and electrical characteristics required for thin-film transistor applications. Further optimization of ZnO microstructure, defect concentration, dielectric/interface quality and deposition conditions could improve carrier transport and switching characteristics. Keyword: Zinc oxide; thin-film transistor; anodized aluminium oxide; gate dielectric; field- effect transistor; electrical characterization; oxide semiconductor.

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