Role of Ga2O3–In2O3–ZnO channel composition on the electrical performance of thin-film transistors

In this work we present a study aiming to determine the role of Ga2O3–In2O3–ZnO (GIZO) channel layer composition on the electrical performance and stability exhibited by thin-film transistors (TFTs). The GIZO films were obtained by magnetron sputtering using ceramic targets of different compositions (Ga:In:Zn = 2:2:1, 2:2:2, 2:4:1 and 2:4:2 at.). Structural analysis corroborates the fully amorphous character of the GIZO deposited layers. For the target compositional range used we observe a Zn deficiency on the produced films, which affects the In/Ga atomic concentration ratios. Resistivity and mobility are found to show a general trend against the measured In/Ga ratio that reveals the role played by In and Ga cations on the transport mechanisms. Targets with increased In concentrations (2:4:1 and 2:4:2) allow to obtain the best TFT performances with field effect mobilities reaching values of 53.0 and 51.7 cm2 V−1 s−1, respectively. In addition, the In-richer GIZO compositions result in considerably more stable TFTs, especially under positive gate bias stress conditions. Finally, it is verified that by using a target with a slightly lower In atomic composition (2:4:2 in comparison to 2:4:1), good stability and mobility can be achieved with potentially lower material costs.