Indium-free GZO thin films prepared using plasma-enhanced atomic layer deposition: toward thin film transistor application

Abstract

Indium–gallium–zinc oxide (IGZO) is regarded as one of the most promising materials to meet the requirements of thin film transistors (TFTs). However, the high cost and environmental danger of indium limit its commercial application. Moreover, the quaternary compound cannot be easily made using thin-film deposition. In this work, GZO thin films without indium have been prepared as a channel layer in TFTs using plasma-enhanced atomic layer deposition (PEALD). The cycle ratio of Ga₂O₃ to ZnO was varied to investigate its impact on the film properties. The GZO films were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), Hall-effect probe measurement and UV-visible spectroscopy. The results of the GZO thin film with 7.5% Ga₂O₃ cycle ratio showed a low carrier concentration of 1.37 × 10¹⁷ cm⁻³ and Hall mobility of 10.67 cm² V⁻¹ s⁻¹. The structural characteristics and electrical characteristics of the GZO channel layer well-align with this conclusion. The I_on/I_off ratio and mobility of TFT based on 7.5% cycle ratio GZO are 1.33 × 10⁶ and 2.6 cm² V⁻¹ s⁻¹, respectively. In this study, the indium-free GZO thin film deposited using PEALD demonstrates great potential for TFT applications.