Simulation and modeling of off-leakage current in InGaZnO thin-film transistors

We investigate the mechanism of off-leakage current in InGaZnO (IGZO) thin-film transistors with the help of a two-dimensional device simulator. The deep donorlike states probably originating from the oxygen vacancies are introduced in the IGZO channel, and it is shown that these trap states significantly affect I-d - V-g characteristics in the off-state region through the pinning of the channel potential. A simple analytical model to explain the simulation results is proposed, which suggests that the off-leak characteristics is controlled by the amount and the depth of the deep donorlike states as well as the thicknesses of IGZO and SiO2 layers in TFT.