This letter discusses the reason for the instability of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) under both positive and negative bias stresses. This instability is significantly influenced by the oxygen content in the bulk IGZO and the surrounding environment. The as-fabricated low-temperature devices can only endure a single polarized bias stress. An a-IGZO TFT that is stable toward both positive and negative bias stresses with large relaxation times of 95 \times 10} 4 and 371times 10 -4 respectively, is achieved by annealing and passivation.
- Bias stress