Characterization of Unpassivated-Solution-Processed Zinc-Tin Oxide Thin Film Transistors

We have studied the bias stress and environment stability effects of transparent bottom-gate, bottom contact spin-coated zinc-tin oxide (ZTO) thin-film transistors (TFT). Various ratios of zinc to tin (Zn : Sn 2 : 1, 1 : 1, and 1 : 2) were used for TFT fabrication. The linear mobilities of the TFTs with Zn : Sn = 2 : 1, 1 : 1, and 1 : 2 are 2.27, 6.77, and 0.44 cm(2) V-1 s(-1) respectively. The on/off drain current ratio is 10(8) for Zn : Sn 2 : 1. However, the off-current increases by more than 5 orders in 7 days, which appears to be due to the adsorption of oxygen and water molecules. The TFTs are stable under negative bias stress for more than 10,000 s, but they show a large threshold shift under positive bias stress. (c) 2011 The Japan Society of Applied Physics