Self-aligned coplanar amorphous indium zinc oxide thin-film transistors (a-IZO TFTs) were fabricated. The a-IZO TFTs had a field-effect mobility of mu(FE) = 24.4 cm(2) V-1 s(-1), a subthreshold slope of 180 mV/dec, and an on/off ratio of 10(9). As the channel length decreased, the threshold voltage V-TH shifted to more negative voltages, and mu(FE) increased due to the diffused carriers from the contact regions. The intrinsic field-effect mobility was estimated to be 15.05 cm(2) V-1 s(-1) in the linear mode and 13.28 cm(2) V-1 s(-1) in saturation mode. Under positive/negative bias-temperature-illumination stress, the shift in V-TH was less than +/- 0.7 V after 11,000 s. (C) 2014 Elsevier Ltd. All rights reserved.