Effect of strontium doping on indium zinc oxide thin film transistors fabricated by low-temperature solution process

Abstract

Solution-processed metal oxide semiconductors for thin film transistors (TFTs) require high-temperature annealing to improve the electrical performance. On the other hand, a high-temperature process cannot be applied to flexible substrates, which is an obstacle preventing the application of MOS films to flexible devices. This paper reports a simple method for improving the electrical characteristics of low-temperature solution-processed indium zinc oxide (IZO) TFTs with strontium (Sr)-doping and vacuum annealing. The addition of Sr to the IZO thin film decreased the density of oxygen vacancies due to the strong bonding energy of Sr with oxygen ions and improved the electrical stability of the IZO TFTs. On the other hand, vacuum annealing increased the number of oxygen vacancies in the IZO film resulting from the low oxygen partial pressure, which led to an increase in carrier concentration. By combining these two methods, Sr-doped IZO TFTs with a high field-effect mobility of 8.75 cm2 V−1 s−1 at 2 mol. % of Sr doping were fabricated.