Enhanced Negative Bias Illumination Stability of ZnO Thin Film Transistors by Using a Two-Step Oxidation Method

In this study, we illustrate a novel way to improve the stability under negative bias illumination stress (NBIS) of ZnO thin-film transistors (TFTs) by adding O-3 treatment after each cycle of growth at 100 degrees C by atomic layer deposition. Compared with the TFTs without O-3 treatment, the shift of threshold voltage (Delta V-th) is reduced from -4.39 to -0.98 V under NBIS, while the mobility decreased from 31.2 to 18.4 cm(2)V(-1)s(-1). By using ZnO (H2O and O-3 as oxidants)/ZnO (H2O as oxidant) bilayer structure, a high filed-effectmobility of 32.1 cm(2)V(-1)s(-1) and an excellent stability (Delta V-th = -2.34 V) have been obtained simultaneously. These improved performance and stabilities are attributed to the bilayer channel structures and the reduction of V-o in the ZnO channel layer treated by O-3.