Effect of the Annealing Ambient on the Electrical Characteristics of the Amorphous InGaZnO Thin Film Transistors

The influence of the thermal annealing on the amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) under different ambient gases has been systematically addressed. The chemical bonding states and transfer characteristics of a-IGZO TFTs show evident dependence on the annealing ambient gas. For the a-IGZO TFTs in the oxygen ambient annealing at 250 °C for 30 mins exhibited a maximum field effect mobility (max μ _FE) of 9.36 cm²/V·s, on/off current ratio of 6.12×10¹⁰, and a subthreshold slope (SS) of 0.21 V/decade. Respectively, the as-deposited ones without annealing possess a max μ _FE of 6.61 cm²/V·s, on/off current ratio of 4.58×10⁸, and a SS of 0.46 V/decade. In contrast, the a-IGZO TFTs annealed at 250 °C for 30 mins in the nitrogen ambient would be degraded to have a max μ _FE of 0.18 cm₂/V·s, on/off current ratio of 2.22×10₄, and a SS of 7.37 V/decade, corresponding. It is attributed to the content of the oxygen vacancies, according the x-ray photoelectron spectroscopy (XPS) analyze of the three different samples.