The Research Of Fabrication And Enhanced Performance For Solution-processed Indium Oxide Thin Film Transistors

The oxide thin film transistors?TFT?has some advances,such as a high mobility,high transmittance and simple preparation process,which conforms to the requirements of the flat panel displays for TFT.With the development of science and technology,many preparation processes for oxide TFT have been developed.The solution process is easy to make a large area,low cost,transparent and multi-component film compared to other preparation process.such as magnetron sputtering,atomic layer deposition,and molecular beam epitaxy,However,the problems of solution-processed oxide TFT,such as a low mobility,large off-state current and poor stability,limit its application in the flat panel displays.Meanwhile,the In₂O₃ TFT is prepared by solution process with the2-methoxyethanol organic solvent in our work,and it is found that the In₂O₃ TFT shows a large off-state current and a poor stability.In order to improve the performance and stability of In₂O₃ TFT,this paper presents a method to inhibit the generation of oxygen vacancy for In₂O₃ thin film by Mg,La and other metal cations addition,which optimizes the interface defect state,and establishes the relationship among the doping concentration,oxygen vacancy,electrical performance and stability.In order to further reduce the threshold voltage of the TFT and improve the process compatibility,the paper use the solution processed high dielectric constant insulating layer to explore the interfacial characteristics between the insulating layer and active layer.Because the 2-methoxyethanol organic solvent is not friendly to the environment and requires high temperature annealing process,the novel In YO TFT is prepared by a green and safe aqueous solution process.The physical mechanism of enhanced performance and stability for the aqueous solution In YO TFT is investigated.The main content and innovations of this paper are as follows:1.The In₂O₃ TFT with Mg addition is prepared by solution process.The results show that the electrical properties and stability of MgInO TFT are improved obviously with the increase of Mg doping concentrations.The Mg InO TFT with 0.75 mol%Mg doping concentration shows the excellent electrical properties(13.77 cm²V^-1s^-1of mobility,2.84 V of threshold voltage and 0.85V/dec of subthreshold swing)and better temperature and bias stability.The enhanced performance of Mg InO TFT is mainly attributed to the reduction of oxygen vacancy by Mg addition.2.The LaInO TFT based on ZrO₂ insulating layer is prepared by solution process.The results show that In₂O₃ TFT has a higher mobility,but the temperature and bias stability of LaInO TFT are poor.With the increase of La doping concentrations,the mobility decreases from 48.8 to 32.7 cm²v^-1s^-1,and the threshold voltage increases from 1.12 to 1.76 V.When La doping concentration is 10 mol%,the LaInO TFT has a small subthreshold swing?0.12 v/dec?.Meanwhile,stability has also been significantly improved.Because the La-O strong bond cooperation can cause the reduction of oxygen vacancy.The XPS results also show that La addition can effectively inhibit the generation of oxygen vacancies and lead to a reduction of defect state.3.The performance of In₂O₃ TFT with solution-processed YAlO insulating layer are studied.When Al elements are added into Y₂O₃ insulating layer,the moisture resistance of the Y₂O₃ insulating layer can be enhanced,the interface roughness between insulating layer and active layer is reduced,and the defect density at the interface is reduced.The average root means square surface roughness?RMS?of the Y₂O₃ thin film is 0.76 nm,which shows a large surface roughness.With the Al doping concentration varying from 5 mol%?Al/?Y+Al??to 15 mol%,the RMS decrease from 0.52 to 0.25 nm.Meanwhile,the electrical properties and stability of In₂O₃ TFT have been significantly improved.The In₂O₃ TFT with 15 mol%Al/?Y+Al?shows a high mobility(19.5 cm²v^-1s^-1)and low threshold voltage?1.58 V?.4.A novel InYO thin film has been prepared by the aqueous solution process of health,safety and environmental protection,and the influence of the Y element doping concentrations on the stability of the In₂O₃ TFT is studied.The results show that the mobility of InYO TFT decreases with the increase of Y doping concentration.The positive bias and illumination negative bias stability of In₂O₃ TFT are improved markedly.When the Y doping concentration is 4mol%,the InYO TFT shows the smallest threshold voltage shift of 0.23 V and0.86 V under positive bias and illumination negative bias stress,respectively.The density of oxygen vacancy and defect state are analyzed by XPS analysis.It is found that the improved stability is mainly due to the Y element addition which can effectively inhibit the generation of oxygen vacancy and reduce the defect density.