Effect of the Active Layer Thickness on the Negative Bias Illumination Stress-induced Instability in Amorphous InGaZnO Thin-film Transistors

The effect of the active layer thickness (T-IGZO) on the negative bias illumanation stress (NBIS)-induced threshold voltage shift (Delta V-T) in amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) is investigated and explained by using a subgap density-of-states model. The NBIS-induced Delta V-T in a-IGZO TFT with a thinner T-IGZO is negatively larger than that in a-IGZO TFTs with a thicker T-IGZO. The T-IGZO-dependent Delta V-T is found to be caused by either hole trapping into the gate insulator near the interface or oxygen vacancy (Vo) ionization, which is activated more by a larger surface electric field E-IGZO as T-IGZO becomes thinner.