Two-step degradation of a-InGaZnO thin film transistors under DC bias stress

Abstract A unified explanation is proposed to consistently explain the two-step degradation of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) under DC positive bias temperature instability (PBTI) stress without or with different drain stress voltages ( V ds ). For PBTI stress without stress V ds , this initial negative V th shift is believed to be induced by donor-like defect states corresponding to H 2 O molecule and intrinsic defects, while for PBTI stress with stress V ds , the negative shift is believed to be induced by donor-like defect states corresponding to oxygen vacancies. The gate-bias-induced electron trapping mechanism is responsible for positive V th shift. These transitions from negative to positive V th shift are resulted from the competition between the donor-like states creation and electron trapping.