Films Stoichiometry Effects on the Electronic Transport Properties of Solution-Processed Yttrium Doped Indium–Zinc Oxide Crystalline Semiconductors for Thin Film Transistor Applications

Spray-coated crystalline InZnO_x-based semiconductors are investigated as a function of [In³⁺]:[Zn²⁺] and their performance as TFTs semiconducting channels. More precisely, it is demonstrated that optical, structural, and electron transport properties show a high degree of sensitivity to the films' stoichiometry; that is, the [In³⁺]:[Zn²⁺] atomic ratio that equally determines the amorphous or crystalline structure of the film. Yttrium co-doping of InZnO_x with [In³⁺]:[Zn²⁺] atomic ratio of 6:4 shows that the YInZnO_x structure and the key TFT parameters can further be engineered and improved in terms of the on-to-off current modulation ratio and, most importantly, the field effect mobility. It is finally demonstrated that the latter is in excess of 52 cm² V^-1 s^-1 by combining crystalline YInZnO_x and spray-coated MgO dielectrics. These results identify spray-coated crystalline YInZnO_x as a viable TFT semiconducting channel material with respect to enhanced electrical performance and processing requirements in terms of simplicity and cost.