Highly Transparent and Conductive W-Doped ZnO/Cu/W-Doped ZnO Multilayer Source/Drain Electrodes for Metal-Oxide Thin-Film Transistors

Here, we demonstrate transparent and conductive W-doped ZnO (WZO)/Cu/WZO multilayer films as source/drain (S/D) electrodes for metal-oxide thin-film transistors (TFTs). The effect of the Cu interlayer thickness on the electrical and optical properties of the films was first investigated. Optimized WZO/Cu/WZO films with an excellent sheet resistance of 4.1Ω/sq. and an average transmittance of 81.7% in the visible range were obtained and employed as the S/D electrodes. Compared with indium-gallium-zinc oxide (IGZO) TFTs with Cu or WZO S/D electrodes, TFTs with multilayer WZO/Cu/WZO S/D electrodes exhibit much better performance with the current ON/OFF ratio, threshold voltage, subthreshold swing, and electron mobility of 10
⁵
, 0.2 V, 0.1 V/dec, and 31.2 cm
²
/Vs, respectively. Owing to the suppression of copper diffusion and low contact resistance between IGZO and WZO/Cu/WZO multilayer films, they can be used as novel S/D electrodes for high-performance fully transparent TFTs.