Enhanced Stability of Solution-Processed Indium–Zinc–Tin–Oxide Transistors by Tantalum Cation Doping

Abstract

Highly stable metal oxide thin film transistors (TFTs) are required in high-resolution displays and sensors. Here, we adopt a tantalum cation (Ta5+) doping method to improve the stability of zinc–tin–oxide (ZnSnO) TFTs. The results show that Ta5+-doped TaZnSnO TFT with 1 mol% concentration exhibits excellent stability. Compared with the undoped device, the oxygen vacancy defects of TaZnSnO thin films reduce from 38.05% to 18.70%, and the threshold voltage shift (ΔVth) reduces from 2.36 to 0.71 V under positive bias stress. We attribute the improved stability to the effective suppression of the oxygen vacancy defects, which is confirmed by the XPS results. In addition, we also prepared TaInZnSnO TFT devices with 1 mol% Ta5+ doping concentration. Compared with the 1 mol% Ta5+-doped TaZnSnO TFTs, the μ increases two-fold from 0.12 to 0.24 cm2/Vs, and the Vth decreases from 2.29 to 0.76 V in 1 mol% Ta5+-doped TaInZnSnO TFT with an In:Zn:Sn ratio of 4:4:3, while the device remains highly stable with a ΔVth of only 0.90 V. The injection of Ta5+ provides a novel strategy for the enhancement of the stability in ZnSnO-based TFTs.