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 V_TH was 9.16 V, the subthreshold swing (SS) was 0.88 V/decade, and the on/off-current ratio was approximately 1 × 10⁸. V_TH 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.