Fabrication and Characterization of High-Performance Thin-Film Transistors Based on Epitaxial Ta-Doped TiO2 Films

Abstract

Ta-doped TiO2 (TiO2:Ta) films were synthesized on MgAl6O10 substrates by the metal-organic chemical vapor deposition (MOCVD) method. The doping uniformities, crystallization qualities, and optical properties of the deposited films were systematically characterized. The measurement results revealed the TiO2:Ta films with low Ta concentrations to be epitaxial anatase films with high transparency in the visible region. Thin-film transistors (TFTs) based on TiO2:Ta films were fabricated. The device with 0.5-at.% Ta-doped TiO2 as a channel layer exhibited clear n-type TFT behaviors with a high ${I} _{ \mathrm{\scriptscriptstyle ON}}/{I} _{ \mathrm{\scriptscriptstyle OFF}}$ ratio of $4.0\times 10^{{8}}$ , a low subthreshold swing of 0.60 V/decade, and a saturation mobility of 4.4 cm2V−1s−1. These parameters were superior to the values of previously reported TiO2-based devices and indicated that the Ta-doped TiO2 film was a promising channel material for transparent metal–oxide TFTs.