Enhanced Electrical Properties and Stability of Solution-processed Amorphous Oxide Thin Film Transistors with Multi-active Layers

We investigated the electrical properties and gate bias stress stability of solution-processed amorphous oxide thin film transistors (TFTs) with multi-stacked active layers. With the multi-layered InZnO (In:Zn = 1:1), mobility was increased from 4.6 to 21.2 cm2V-1s-1 and the subthreshold swing (SS) was improved from 0.71 to 0.54 V/decade compared to the single-layered InZnO TFT. The tri-layered InZnO TFT showed a reduced threshold voltage shift (ΔVth) under positive bias stress (PBS) from +4.4 to + 0.9 V, whereas ΔVth under negative bias stress (NBS) deteriorated from -0.03 to -1.5 V. We also fabricated bi-layered (bottom/top layer) TFTs using different oxide compositions with InZnO (In:Zn = 7:3) and InGaZnO (In:Zn:Ga = 3:3:1) which showed high mobility and small ΔVth under PBS and NBS. The InZnO/InGaZnO TFT showed a high mobility of 17 cm2V-1s-1, SS of 0.65 V/decade, and good stability, with ΔVth under PBS and NBS of +1.2 and -1.2 V, respectively. Both the electrical properties and gate bias stress (GBS) stability were better with the InZnO/InGaZnO TFT than the single-layered InZnO TFT.