Feasibility of ZnO:Al/Ag/ZnO:Al multilayer source/drain electrode to achieve fully transparent HfInZnO thin film transistor

We fabricated fully transparent hafnium indium zinc oxide (HfInZnO) thin film transistors (TFTs) with ZnO:Al(AZO)/Ag/ZnO:Al multilayer source/drain (S/D) electrodes. The effect of Ag interlayer thickness on the electrical and optical properties of AZO(60 nm)/Ag/AZO(60 nm) multilayer films was investigated. The AZO(60 nm)/Ag(10 nm)/AZO(60 nm) multilayer film shows a low sheet resistance of 10.5 Ω/square and a transmittance of 87%. Compared with HfInZnO-TFT with AZO electrode, the performance of the device with AZO/Ag/AZO multilayer electrode was significantly improved. The field effect mobility increased from 3.2 to 5.8 cm 2 /V s, and the threshold voltage reduced from 2.3 to 0.1 V. The improvement was attributed to the lower resistivity of AZO/Ag/AZO multilayer film. The result indicates that AZO/Ag/AZO multilayer electrode is a promising S/D electrode for fully transparent HfInZnO-TFTs.