Density of trap states measured by photon probe into ZnO based thin-film transistors

We report on photo-excited trap-charge-collection spectroscopy, contrived to measure the density of deep-level traps near channel/dielectric interface in a working ZnO based thin-film transistor as a function of photon probe energy. Free charges trapped at a certain energy level are liberated by the correspondingly energetic photons and then electrically collected at the source/drain electrodes. During this photo-electric process, the threshold voltage of TFT shifts and its magnitude provides the density-of-state information of charge traps. In the present work, we directly characterized the density-of-state of ZnO based thin-film transistors with polymer-oxide double dielectrics after evaluating their gate stabilities.