Electrical Performance and Stability Improvement of p-Channel SnO Thin-Film Transistors Using Atomic-Layer-Deposited Al₂O₃ Capping Layer

The incorporation of an atomic-layer-deposited Al<sub>2</sub>O<sub>3</sub> capping layer was proposed as an effective method to enhance the electrical performance and stability of p-channel SnO thin-film transistors (TFTs). The SnO TFT with the Al<sub>2</sub>O<sub>3</sub> capping layer demonstrated better electrical characteristics, such as higher field-effect mobility (<inline-formula> <tex-math notation="LaTeX">$\mu _{\mathrm {FE}} =1.7$ </tex-math></inline-formula> cm<sup>2</sup>/<inline-formula> <tex-math notation="LaTeX">$\text{V}\cdot \text{s}$ </tex-math></inline-formula>), smaller subthreshold swing (<italic>SS</italic> =2.9 V/dec), and larger current on/off ratio (<inline-formula> <tex-math notation="LaTeX">$I_{\mathrm {ON/OFF}} = 1.6\times 10^{4}$ </tex-math></inline-formula>), than the pristine SnO TFT (<inline-formula> <tex-math notation="LaTeX">$\mu _{\mathrm {FE}} =1.5$ </tex-math></inline-formula> cm<sup>2</sup>/<inline-formula> <tex-math notation="LaTeX">$\text{V}\cdot \text{s}$ </tex-math></inline-formula>, <italic>SS</italic> =3.8 V/dec, and <inline-formula> <tex-math notation="LaTeX">$I_{\mathrm {ON/OFF}} = 6.9\times 10^{2}$ </tex-math></inline-formula>). Furthermore, the Al<sub>2</sub>O<sub>3</sub>-capped SnO TFT exhibited significantly enhanced electrical stability under an applied negative-gate-bias stress compared to the pristine device. The observed phenomena were mainly attributed to the decreased number of oxygen-vacancy-induced hole trap states within the SnO owing to diffused hydrogen from the atomic-layer-deposited Al<sub>2</sub>O<sub>3</sub> layer. Our experimental results thus demonstrate that incorporating the atomic-layer-deposited Al<sub>2</sub>O<sub>3</sub> capping layer is a simple and effective method for improving the electrical characteristics of p-channel SnO TFTs.

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