Effects of low-temperature (120 degrees C) annealing on the carrier concentration and trap density in amorphous indium gallium zinc oxide thin film transistors

Abstract

We report an investigation of the effects of low-temperature annealing on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). X-ray photoelectron spectroscopy was used to characterize the charge carrier concentration, which is related to the density of oxygen vacancies. The field-effect mobility was found to decrease as a function of the charge carrier concentration, owing to the presence of band-tail states. By employing the transmission line method, we show that the contact resistance did not significantly contribute to the changes in device performance after annealing. In addition, using low-frequency noise analyses, we found that the trap density decreased by a factor of 10 following annealing at 120 degrees C. The switching operation and on/off ratio of the a-IGZO TFTs improved considerably after low-temperature annealing. (C) 2014 AIP Publishing LLC.