Improved Electrical and Thermal Stability of Solution-Processed Li-Doped ZnO Thin-Film Transistors

The effects of lithium (Li) doping on the performance of solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) grown using the sol-gel method are investigated. Li-doped ZnO films as channel layers are chemically prepared by spin coating the gel with an aqueous solution of zinc acetate dihydrate, Li nitrate, and ethanolamine. TFT devices fabricated with 2 at.% Li-doped films show a good field-effect mobility of 3.31 cm²/V·s, a subthreshold slope of 0.82 V/dec, and an on-off current ratio of over 10⁵. These TFT devices also show good thermal and electrical stability, which is mainly attributed to the compact surface morphology of the channel layer, small carrier concentration, and less oxygen deficiency, which reduces the interface electrical trapping at the gate insulator.