Effect of Oxygen on the Optical and the Electrical Properties of Amorphous InGaZnO Thin Films Prepared by RF Magnetron Sputtering

Abstract
To investigate the effect of oxygen on the optical and the electrical properties of amorphous InGaZnO (a-IGZO), we prepared thin films by RF magnetron sputtering in various oxygen atmospheres at room temperature and the thin-film transistors (TFTs) were evaluated. The oxygen concentration during the deposition process affected both the optical band-gap and the mobility of a-IGZO-based devices. As the oxygen concentration in the processing chamber during deposition was increased, the optical band-gap and the saturation mobility decreased concurrently. The highest optical band-gap and the best device performance were obtained from the a-IGZO film deposited in an atmosphere of 10 \% oxygen. The a-IGZO film deposited at this condition exhibited an optical band-gap of 3.29 eV and the transistors fabricated with this film revealed a saturation mobility of 2.6 cm$^2$/V$cdot$s, a subthreshold swing of 0.93 V/decade, an on-off current ratio of 10$^7$ and a threshold voltage of 13.9 V.
Keywords: Oxide semiconductor, Amorphous InGaZnO (a-IGZO), RF sputtering, Optical properties, Thin-film transistor, Electrical characteristics

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