SrTa2O6 induced low voltage operation of InGaZnO thin-film transistors

High-k amorphous SrTa2O6 (STA) thin films were successfully deposited by rf magnetron sputtering for gate insulators in thin-film transistor (TFT). Practical STA thin films with high dielectric constant of 41.8, wide band gap of 4.58 eV, and low leakage current of ~10−8 A/cm2 were obtained through by optimal sputtering condition. The TFTs with amorphous InGaZnO (IGZO) as a channel and STA as a gate insulator were fabricated and investigated for thinning effects of gate insulator on transfer characteristic. The IGZO-TFT with 70-nm-thick STA achieved high performance switching properties; (mobility of 14.9 cm2/(V·s), threshold voltage of 0.6 V, sub-threshold swing of 111 mV/decade, and on/off ratio of 1.0 × 1010). These characteristics are due to the large gate capacitance of 4.6 × 10−7 F/cm2 and low gate leakage current from use of STA.