Reliability of Crystalline Indium-Gallium-Zinc-Oxide Thin-Film Transistors Under Bias Stress With Light Illumination

We investigate the effect of crystalline indium-gallium-zinc-oxide (c-IGZO) thin films on device performance, and evaluate the device reliability of c-IGZO under positive/negative bias stress with/without illumination. The crystal structure of deposited-IGZO thin film is controlled by annealing temperatures, and the transition from an amorphous to a crystalline structure is observed at above 800 degrees C. Even though the c-IGZO thin-film transistors (TFTs) exhibit lower carrier mobility, compared with amorphous IGZO (a-IGZO) TFTs, the remarkable improvement of the device reliability for the c-IGZO TFTs is observed especially under the bias stress with illumination. This comes from lower defect density compared with the a-IGZO film.