Enhanced Stability Performance of Transparent Ozone ALD ZnO Thin-Film Transistors With SiAlO_X Dielectric

A new method is proposed to improve the stability performance of zinc oxide (ZnO) thin-film transistors (TFTs) by reducing density of oxygen vacancies and enlarging valance band offset (VBO) between channel/insulator simultaneously. At first, ozone (O3) is used as oxidant during the atomic layer deposition (ALD) of ZnO to reduce its oxygen vacancies from 22.64% to 14.32%, compared with the oxidant of H2O, resulting in less shift of threshold voltage ( $\boldsymbol {\Delta }{V}_{\text {TH}}$ ) under negative bias stress with illumination (NBIS). To further improve the stability of TFTs under NBIS, Al2O3 layer is replaced by SiO2 to obtain larger VBO, but it introduces worse interface quality with larger hysteresis window (~0.57 V). Hence, a compound dielectric layer SiAlO $_{X}$ is proposed and prepared by ALD to improve the interface quality of ZnO/insulator. Combining O3 ALD ZnO and SiAlO $_{X}$ dielectric, the ZnO TFTs exhibit a high saturation mobility of 43.8 cm $^{{2}}\cdot \text{V}^{-1}\cdot \text{s}^{-{1}}$ , a negligible hysteresis window (< 0.01 V), and excellent stability under various stresses, especially under NBIS ( $\boldsymbol {\Delta }{V}_{\text {TH}}= -1.09$ V).