Characteristics of amorphous transparent InGaZn₆O₉ electrodes prepared by RF-magnetron sputtering for fully transparent thin film transistors

We have investigated the properties of InGaZn₆O₉ thin films fabricated by radio frequency (RF) magnetron sputtering for the application to the electrodes in transparent thin film transistor (TTFT). The InGaZn₆O₉ thin films have been prepared with varying working pressure and RF power. It has been found that the InGaZn₆O₉ films have an amorphous structure and show a very smooth and featureless surface regardless of the deposition conditions. At optimized deposition condition, the InGaZn₆O₉ film shows an average transmittance of about 83.54% in the visible region and the sheet resistance of about 91.6 Ω/sq. The top gate InGaZnO₄ TTFT device embedded with InGaZn₆O₉ electrode operates in enhanced mode with a threshold voltage of 1.1 V, a mobility of 3.48 cm²/Vs, an on-off ratio of > 10⁴, and a sub-threshold slope of 0.9 V/decade. In addition, the optical transmittance of the TTFT device is observed about 85% at 550 nm wavelength.