Gas adsorption effects on electrical properties of amorphous In2O3 thin-film transistors under various environments

Abstract

We report the electrical properties of amorphous In2O3 thin-film transistors (TFTs) measured under various environments without annealing treatment. Although the as-deposited TFT showed superior semiconducting properties in air (μsat: 32.7 cm2 V−1 s−1, Ion/Ioff: 4.2 × 108, ss: 0.54 V/dec), its current–voltage (I–V) characteristics changed drastically after evacuation. The capacitance–voltage (C–V) characterization revealed that the transition of the TFT properties from semiconducting to metallic might be caused by the reduction of electron trap states. In addition, the observed peak C–V behavior suggested that large amounts of oxygen ion impurities are included in the film that may not diffuse out even after evacuation. The transition of the TFT properties is thus caused by O2 desorption due to the In2O3 on the surface rather than that inside the film. The large amounts of ion impurities present in the as-deposited In2O3 film need to be controlled for the realization of future room-temperature TFT fabrication technology.