| Summary: | Degradation behaviors of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) under negative bias stress (NBS) and negative bias illumination stress (NBIS) are investigated systematically. In some cases, a two-stage degradation behavior of a-IGZO TFTs is observed under both NBS and NBIS, which begins with a small positive shift of threshold voltage (V<sub>th</sub>), and is followed by a large negative V<sub>th</sub> shift. There is an intrinsic correlation between the degradations of NBS and NBIS. Quantitatively, both stress gate biases (V<sub>G</sub>) and temperature dependencies of ΔV<sub>th</sub> of the two degradations are found to be the same and the recovery processes are also very similar. A unified model of NBS and NBIS is proposed to consistently explain the degradation behaviors of a-IGZO TFTs and their correlation.
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