Transistor characteristics of zinc oxide active layers at various zinc acetate dihydrate solution concentrations of zinc oxide thin-film

 

H.C. You

 

Department of Electronic Engineering, National Chin-Yi University of Technology, Taiwan. E-mail address: hcyou@ncut.edu.tw

 

Abstract

This paper presents a technique involving a sol-gel deposition method applied to the deposition of zinc oxide thin film for a transistor as a semiconductor layer. This method was used for manufacturing the essential thin films of II-VI semiconductors. Zinc oxide (ZnO) bottom-gate (BG) thin-film transistors (TFTs) have been successfully fabricated at low temperatures. We investigated the electrical characteristics of ZnO thin-film transistors at various concentrations of ZnO solution: 0.02 M, 0.03 M, 0.04 M, and 0.05 M. All of the ZnO films exhibited a hexagonal wurtzite polycrystalline structure with (002) preferred orientation. Atomic force microscopy (AFM) revealed the formation of grains or clusters as a result of the accumulation of nanoparticles, and the grain size increased with increasing solution concentration. The coated ZnO films were employed as the active channel layer in thin-film transistors, and the impact of the solution concentration on the device performance was examined. As the solution concentration was increased, the field-effect mobility increased from 1 x 10^-4 cm²/V-s to 1.2 x 10^-1 cm²/V-s, the threshold voltage increased from 4.8 V to 11.1 V, and the I_on/I_off ratio increased from 10⁴ to 10⁶. The on-off ratio (I_on/_off) was found to be 10⁶. The 0.05 M ZnO solution performed optimally.

Keywords: ZnO; Zinc acetate dihydrate solution; Thin-film transistor; Concentration.

 

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Acknowledgments

This work was supported by the National Science Council, Taiwan, under Contract Nos. MOST 103-2221-E-167-035.

 

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