High performance of ZnSnO thin-film transistors engineered by oxygen defect modulation

Abstract

Thin film transistor (TFT) with low cost and high performance is significantly important for practical applications. In this work, In-free ZnSnO (ZTO) TFT with high performance is achieved by modulating the annealing atmosphere to manipulate the amount and charge state of oxygen defect, and then the effects of annealing atmosphere are systematically investigated by experiment and theoretical calculation. Results show that, O2 condition results in an inferior electron mobility although the formation of oxygen defect is suppressed. The oxygen vacancies created in N2 ambience are most probably dominated by neutral ones that limit the electron transport. The ZTO TFT dealt with vacuum condition exhibits the best performances, i.e. μlin, Vth, SS and Ion/Ioff are 19.80 cm2/Vs, 0.05 V, 0.46 V/dec and 108, respectively, which can be attributed to the cooperation of the decreased RC and RSH, the charge-state transition of oxygen defect. Further investigation indicates that, doubly charged oxygen vacancy not only results in the elevation of electron content and thus reduce the conduction barrier, but also shrinks the supercell volume to maintain the highly dispersed conduction band, which is crucially important for the electron transport. The findings may facilitate the ability to engineer other high performance AOS materials and devices.