Influence of structural defects in solution-processed InZnO semiconductors on the electrical stability of thin-film transistors

In this study, we investigate the morphological effect of solution-processed indium-zinc-oxide (InZnO) active layers on the electrical stability of InZnO thin-film transistors (TFTs). We first observe that in the spin-coating method, precursor agglomerates and aggregates remain on the substrates after spin coating an InZnO solution at a low spin speed, thereby causing particle-type morphological defects in the InZnO films. The morphological defects are proven to degrade the basic performance parameters of the InZnO TFTs, including the electrical current level, field-effect mobility, and threshold voltage. In addition, devices having morphological defects show a relatively large hysteresis in transfer characteristics compared to those without defects. In a test of the electrical stability over time, we determine that particle-type morphological defects cause a rapid increase in the conductivity of the InZnO films, which affects the variations in the saturation drain current and the threshold voltage.