Channel migration of dual channel a-InGaZnO TFTs under negative bias illumination stress

Abstract

In this work, the time-dependent behaviors of dual-channel amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) under negative bias illumination stress (NBIS) are systematically discussed. The dual-channel comprised two different IGZO layers fabricated by tuning the oxygen flow during deposition. The presence of heterojunctions enhanced field-effect mobility by 1.5× owing to the confinement of carriers in buried channels because of an energy barrier. However, after long periods of NBIS stress, the degradation of a-IGZO TFTs resulted in the entrapment of photo-generated electron–hole pairs at interface defects. The conduction path migrated to the surface channel. Results from extracting the hysteresis window and utilizing capacitance–voltage measurements have indicated a channel migration phenomenon due to the entrapment of electrons and holes at the surface and buried channel interfaces.