The Fabrication And Investigation Of High-performance Metal Oxide Thin-Film Transistors

In recent years,the metal oxide semiconductor thin film transistor(TFT) has shown great application prospects due to its advantages of low preparation temperature,good stability,compatibility with flexible substrates,high mobility and low cost,and it has been extensively studied.Metal oxide thin films are generally prepared by vacuum technologies such as magnetron sputtering and pulsed laser deposition.However,with the rapid growth of demand for cost-effective and large-area electronic products,thin film transistors need to be integrated at low cost.The solution method has become a more competitive choice because of its advantages such as simplicity,economy,good uniformity,and manufacturing in the atmosphere.It is suitable for preparing large-area flexible electronic products,such as flexible displays and smart wearable devices.This paper focuses on the research of n-type oxide thin film transistors prepared by the solution method.The main content and results focus on the following two aspects:(1)IGO thin film transistors with different In contents are prepared by using the aqueous solution method at an annealing temperature of 450°C.AFM,XRD,PL,XPS and other tests were performed on IGO films.The results show that the thin films of different components are amorphous,with few clusters,uniform and smooth surfaces with the root-mean-square roughness in the nanometer range,which is beneficial to obtain highly uniform oxide films.The increase of In content can increase the oxygen vacancies and deep-level trap states in the metal oxide lattice,and reduce the band gap of the film.When the molar ratio of In to Ga is 1:1,the band width is 4.25 eV.In addition,the increase of In content can increase the number of M-O bonds in the metal oxide lattice,which enhances the conductivity of the film.The thin-film transistor with the structure of bottom-gate top contact can be prepared by depositing Al electrodes on IGO thin films.Electrical analysis shows that the IGO thin-film transistors have the characteristics of n-channel field effect transistors.With the increase of the In content,the saturation mobility and switching current ratio increase,the defect density in the channel decreases,and the saturation current of the device increases from n A to m A.When the molar ratio of In to Ga is 1:1,the ?_sat of the IGO thin film transistor is 3.63 cm²V^-1s^-1,the I_on/I_of reaches 10⁶,and the V_th is 2.5 V,and the device shows good field effect characteristics.The above results show that In doping can significantly improve the performance of metal oxide thin film transistors prepared by the solution method under low temperature annealing conditions.(2)AlGaO thin films were prepared by the aqueous solution method under low temperature annealing conditions.It is found that the films of different components are all amorphous and the surfaces are very smooth.The smooth surface can form good interface contact between the gate insulating layers and the channel layers.The transmittance of the thin film is above 98% when the wavelength of incident light is between 380 nm and 780 nm.As the Al doping concentration increases,the band gap of the thin film gradually increases.The leakage currents of the thin films are low due to the good surface morphology of the AlGaO thin films.When the thin films are used as the insulating layers,the number of defects in the channel layer and the static power consumption can be reduced.The capacitances of the films are higher at low frequencies and decrease at high frequencies,which indicates that there are more defects in AlGaO films prepared by the solution method.The IZO precursor solution is deposited on the thin film which is annealed at 300°C with a molar ratio of Al to Ga of 1:1.After the electrodes are thermally evaporated,the thin-film transistors with the structure of bottom-gate top contact are prepared.The devices have the characteristics of n-channel field effect transistors,the saturated mobility is 7.7 cm²V^-1s^-1,the threshold voltage is 0.2 V,and the switching current ratio is 2.7×10⁴.The above results show that when AlGaO is used as the gate insulating layers,the gate voltage can effectively control the conductivity of the channel layer and modulate the source-drain current.Therefore,the switching state of the thin film transistor is realized.