Effect of structural relaxation (SR) on the electrical characteristics and bias stability of solution-processed zinc-tin oxide (ZTO) thin-film transistors (TFTs) were systematically investigated by controlling the annealing time of the ZTO semiconductor films. Note that SR was found to increase with increased annealing time. Due to the increased SR, the ratio of oxygen vacancies (VO) increased from 21.5% to 38.2%. According to increased VO, the mobility in the saturation region was exhibited by a sixfold increase from 0.38 to 2.41 cm2 V-1 s-1. In addition, we found that the threshold voltage negatively shifted from 3.08 to -0.95 V. Regarding the issue of bias stability, according to increased SR, positive-bias stress of the ZTO TFTs was enhanced, compared with reverse features of negative-bias stress. Our understanding is expected to provide a basic way to improve the electrical characteristics and bias stability of rare-metal-free oxide semiconductor TFTs, which have not been sufficiently studied.
Keywords: bias stability; electrical characteristics; solution process; structural relaxation; thin-film transistor; zinc–tin oxide.