High-performance indium gallium zinc oxide transparent thin-film transistors fabricated by radio-frequency sputtering

Thin-film transistors (TFTs) based on amorphous indium gallium zinc oxide (a-IGZO) were fabricated by radio-frequency magnetron sputtering on glass substrates. The TFT device structure was a bottom-gate type, consisting of indium zinc oxide and HfO2 as electrodes (gate, source, and drain) and gate dielectric, respectively. The resistivity of the a-IGZO channel layer was ∼1 cm. TFTs with a 6 μm gate length and 100 μm gate width displayed a saturation mobility of ∼7.2 cm2 V-1 s-1, a threshold voltage of 0.44 V, a drain current on-off ratio of ∼ 105, and subthreshold gate-voltage swing of ∼0.25 V decade-1. After 1000 h aging time at room temperature, the saturation mobility remained almost constant while the threshold voltage shift was as small as 460 mV. The IGZO TFTs based on HfO2 gate dielectrics sputtered near room temperature were found to be good candidates for applications on organic flexible substrates.