Environmentally and Electrically Stable Sol–Gel-Deposited SnO₂ Thin-Film Transistors with Controlled Passivation Layer Diffusion Penetration Depth That Minimizes Mobility Degradation

This study examines the effect of the annealing time of the Y2O3 passivation layer on the electrical performances and bias stabilities of sol–gel-deposited SnO2 thin-film transistors (TFTs). The environmental stabilities of SnO2 TFTs were examined. After optimizing the Y2O3 passivation layers in SnO2 TFTs, the field-effect mobility was 7.59 cm2/V•s, the VTH was 9.16 V, the subthreshold swing (SS) was 0.88 V/decade, and the on/off-current ratio was approximately 1 × 108. VTH shifts were only −0.18 and +0.06 V under negative and positive bias stresses, respectively. The SnO2 channel layer thickness and oxygen-vacancy concentration in SnO2, which determine the carrier concentration, were successfully tuned by controlling the annealing time of the Y2O3 passivation layers. An extremely thin Y2O3 passivation layer effectively blocked external molecules, thus affecting the device performance. The electrical performance was maximized in SnO2 TFTs using a 15 min-annealed Y2O3 passivation layer. In this TFT, the field-effect mobility was maximally retained and the bias and environmental stabilities were sustained over 90 days of air exposure.