The optical and electrical properties of amorphous gallium/titanium co-doped indium oxide films based on oxygen flow dependence

Amorphous gallium/titanium (Ga,Ti) co-doped indium oxide (In2O3) (GTiIO) films present significant potential as transparent conducting electrodes for use in flexible electronic devices. Amorphous GTiIO films were grown on silicon and glass substrates using linear-facing target sputtering and various oxygen flow rates. Transmittance was as high as 80% in the visible range for O2 flow rates of 0.3, 0.7, and 1.0 SCCM. The lowest resistivity was obtained at f(O2) = 0.3 SCCM with 0.47 mΩ cm. Dielectric functions were determined, and optical gap energies were estimated as close to 3.4 eV using a Tauc formula. We show that Drude tail amplitude is proportional to the carrier density. An electronic transition was found at 2.7 eV from the optical spectra of the thin film at f(O2) = 0 SCCM; this transition was designated to be an inter-conduction band transition from the first to the second conduction band. Using Hall parameters and Drude tail amplitudes in dielectric functions, the effective mass of GTiIO films was determined as 0.398 m0 at f(O2) = 0.3 SCCM.