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

Abstract

The incorporation of an atomic-layer-deposited Al2O3 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 Al2O3 capping layer demonstrated better electrical characteristics, such as higher field-effect mobility ( $\mu _{\mathrm {FE}} =1.7$ cm2/ $\text{V}\cdot \text{s}$ ), smaller subthreshold swing ( SS =2.9 V/dec), and larger current on/off ratio ( $I_{\mathrm {ON/OFF}} = 1.6\times 10^{4}$ ), than the pristine SnO TFT ( $\mu _{\mathrm {FE}} =1.5$ cm2/ $\text{V}\cdot \text{s}$ , SS =3.8 V/dec, and $I_{\mathrm {ON/OFF}} = 6.9\times 10^{2}$ ). Furthermore, the Al2O3-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 Al2O3 layer. Our experimental results thus demonstrate that incorporating the atomic-layer-deposited Al2O3 capping layer is a simple and effective method for improving the electrical characteristics of p-channel SnO TFTs.