Effect of atmosphere dependent annealing on the preparation and properties of MgZnO thin-film transistors
To investigate the influence of annealing atmosphere on the performance of MgZnO-TFT,MgZnO thin films were prepared by radio frequency magnetron sputtering and used as the channel layer to construct a bottom-gate top-contact structure MgZnO-TFT device.The MgZnO thin films were subjected to annealing treatment at 500℃for 1 h in four different atmospheres,including air,vacuum,oxygen and nitrogen.Atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS)techniques were used to characterize and analyze the thin films.The results show that the MgZnO thin film quality is better after annealing in vacuum atmosphere,and the device performance is the best with a field-effect mobility of 0.29 cm2·V-1·s-1,a threshold voltage of 2.28 V,a subthreshold swing of 3.6 V·dec-1 and a current switching ratio of 1.68×106.The analysis suggests that this may be due to the fact that annealing in vacuum atmosphere can effectively isolate external interference to a certain extent and avoid the generation of defects in the active layer thin film.At the same time,we studied and tested the stability of positive bias stress(PBS)and negative bias stress(NBS)of the device,and the TFT showed good stability under different gate bias stress conditions.When the positive bias pressure is 10 V and the stress time is 3 000 s,the threshold voltage drift of MgZnO-TFT optimized under vacuum atmosphere decreases from 1.38 V to 0.54 V compared with the ZnO-TFT.The results indicate that doping magnesium element into zinc oxide to prepare MgZnO thin films as the active layer of TFT has a certain degree of improvement on the electrical stability of TFT devices.
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