Effects of praseodymium doping on the electrical properties and aging effect of InZnO thin-film transistor

Abstract

Amorphous indium gallium zinc oxide is a popular semiconductor candidate for amorphous oxide semiconductor thin-film transistors in the field of flat-panel display. However, the existence of gallium component restricts the enhancement of mobility dramatically. In this study, we report a new praseodymium (Pr) dopant as a stabilizer in amorphous indium zinc oxide semiconductor (IZO) with high mobility and stability. Meanwhile, the PrIZO TFTs were fabricated to investigate the effects of Pr on electrical properties, stability and aging effect. The optimal PrIZO TFT exhibited a desired performance with a saturation mobility (μsat) of 25.8/32.6 cm2 V−1 s−1, an Ion/Ioff ratio of 3.5 × 107/5.4 × 107, a subthreshold swing value of 0.14/0.13 V dec−1 and a threshold voltage (Vth) of 2.9/2.1 V, respectively, before and after an air environment storage period of 90 days without passivation layer, which exhibits lower sensitivity of the channel region to oxygen/moisture from the atmosphere than IZO TFT. XRD analysis revealed that the Pr dopant had no effect on the amorphous state of IZO thin film with annealing up to 400 °C. XPS analyses suggested that the fraction of oxygen vacancy subpeak decreased significantly with Pr incorporated into IZO. The μ-PCD decay analyzation and the subgap density of states indicate that acceptor-like trap states induced by Pr ions lead to the suppression of ambient-induced excess carrier in conduction band. This work is anticipated to provide a kind of reliable stabilizer for amorphous oxide semiconductor without deteriorating mobility significantly.