High-mobility thin-film transistor with amorphous InGaZnO4 channel fabricated by room temperature rf-magnetron sputtering

Thin-film transistors (TFTs) were fabricated using amorphous indium gallium zinc oxide ($a$ -IGZO) channels by rf-magnetron sputtering at room temperature. The conductivity of the $a$ -IGZO films was controlled from $\sim {10}^{-3}\text{to}{10}^{-6}\mathrm{S}{\mathrm{cm}}^{-1}$ by varying the mixing ratio of sputtering gases, ${\mathrm{O}}_2∕({\mathrm{O}}_2+\mathrm{Ar})$ , from $\sim 3.1\%$ to 3.7%. The top-gate-type TFTs operated in $n$ -type enhancement mode with a field-effect mobility of $12{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ , an on-off current ratio of $\sim {10}^8$ , and a subthreshold gate voltage swing of $0.2\mathrm{V}{\text{decade}}^{-1}$ . It is demonstrated that $a$ -IGZO is an appropriate semiconductor material to produce high-mobility TFTs at low temperatures applicable to flexible substrates by a production-compatible means.