Solution processed F doped ZnO (ZnO:F) for thin film transistors and improved stability through co-doping with alkali metals

Abstract

This paper reports solution-processed metal oxide semiconductor thin film transistors (TFTs), which were produced using fluorine (F) doped ZnO-based aqueous solution. It was found that doping F into the ZnO film improves thin film transparency and TFT performance with an ultrahigh on/off ratio of 10⁸. The F doped ZnO TFT devices showed no improvement in shelf-life stability but improved bias stress stability. Moreover, when the ZnO:F was co-doped with alkali metals like Li, Na, and K, the co-doped ZnO TFT devices exhibited much higher electron mobility, in comparison with ZnO or the ZnO:F TFTs. In addition, the co-doped TFT device exhibited excellent shelf-life stability and bias stress stability. These results suggest that F and alkali metal co-doping can be a useful technique to produce more reliable and low temperature solution-processed ZnO semiconductors for TFTs and their applications.