Mechanism analysis of photoleakage current in ZnO thin-film transistors using device simulation

We analyzed the photoleakage current (I(leak)) in ZnO thin-film transistors using device simulation. The dependences of I(leak) on the location of light irradiation and drain voltage are reproduced by considering a Schottky barrier at the source contact using a two-dimensional device simulation. First, carrier generation is induced by light irradiation, the generated holes accumulate near the source contact, and some of these are captured in the donor traps. Next, the Schottky barrier becomes narrow, and electron injection increases via a tunneling effect. This discussion also suggests that the off-current is exceedingly low because the Schottky barrier prevents electron injection. (C) 2010 American Institute of Physics. [doi:10.1063/1.3502563]