Exploring the photoleakage current and photoinduced negative bias instability in amorphous InGaZnO thin-film transistors with various active layer thicknesses

The photoleakage current and the negative bias and illumination stress (NBIS)-induced instability in amorphous InGaZnO thin-film transistors (a-IGZO TFTs) with various active layer thicknesses (T(IGZO)) were investigated. The photoleakage current was found to gradually increase in a-IGZO TFTs irrespective of the T(IGZO) when the photon energy of visible light irradiation exceeded ≈2.7 eV. Furthermore, the influence of the T(IGZO) on NBIS-induced instability in a-IGZO TFTs was explored by the combination of current–voltage measurements in double-sweeping V(GS) mode and capacitance–voltage measurements. The NBIS-induced hysteresis was quantitatively analyzed using a positive gate pulse mode. When the T(IGZO) was close to the Debye length, the trapped electrons at the etch-stopper/IGZO interface, the trapped holes at the IGZO/gate insulator interface, and the generation of donor-like states in an a-IGZO layer were especially prominent during NBIS.