Effects of Sn Doping on the Electrical Performance and Stability of Sub-V Operating Metal-Oxide Thin-Film Transistors Fabricated by Oxygen Annealing

The incorporation of Sn into a sol-gel-based indium-gallium-zinc oxide (IGZO) channel layer is investigated to improve the electrical characteristics and operational stability of amorphous metal-oxide thin-film transistors (oxide-TFTs). Sub-V operating Sn-doped IGZO-TFTs (IGZTO-TFTs) fabricated by solution-process under a high-pressure oxygen-enriched (O2) atmosphere exhibit significantly improved electrical properties such as a high linear field-effect mobility (11.5 cm2 V−1 s−1), high on/off ratio (up to 108), and low subthreshold swing (0.10 V/dec). The activation energy and density of states are determined to perform comparative analysis on the charge transport characteristics of the IGZTO-TFTs. Under both prolonged positive and negative bias illumination stresses, large shifts in threshold voltages of the IGZO-TFTs are reduced significantly after Sn doping. The suppressed formation of oxygen-related defect states affects the electrical characteristics and operational stability. This is verified by determining the proportional ratio of metal-oxygen bonding states in the O2-annealed IGZTO films.