Electrical Properties of Solution Processed In–Ga–ZnO Thin Film Transistors with Multi-Stacked Active Layer

In this study, we prepared solution-based In–Ga–ZnO thin film transistors (IGZO TFTs) having a multistacked active layer. The solution was prepared using an In:Zn = 1:1 mole ratio with variation in Ga content, and the TFTs were fabricated by stacking layers from the prepared solutions. After we measured the mobility of each stacked layer, the saturation mobility showed values of 0.8, 0.6 and 0.4 (cm²/Vs), with an overall decrease in electrical properties. The interface formed between the each layers affected the current path, resulting in reduced electrical performance. However, when the gate bias V _G = 10 V was applied for 1500 s, the threshold voltage shift decreased in the stack. The uniformity of the active layer was improved in the stacked active layer by filling the hole formed during pre-baking, resulting in improved device stability. Also, the indium ratio was increased to enhance the mobility from 0.86 to 3.47. These results suggest high mobility and high stability devices can be produced with multistacked active layers.