Preparation Of Indium Oxide-based Thin Film By Aqueous Solution Method And Its Application In Thin Film Transistor

In the past decade,thin film transistors(TFTs)have received a lot of attention as important components in flat panel displays(FPD).Especially for transparent metal oxide semiconductors such as In2O3 based(IGZO),the In2O3 TFT has high mobility due to the s orbital of In³⁺is highly spherically symmetric.In addition,the advantages of good uniformity,high transparency,and simple operation make metal oxide semiconductors widely applied in new display driving TFTs.However,In2O3 has large off-state current,negative threshold voltage and poor stability,which limits its application in FPD.Therefore,it is necessary to choose a suitable dopant to improve the on/off current ratio,threshold voltage and stability of the devices.Compared with the traditional vacuum deposition,solution-based approaches have the advantage of being more widely abundant,lower cost,easier to vary chemical stoichiometry,mass productivity and having simplicity path to fabricate thin films.Solution processing initially focused on organic solvent,which is toxic to human beings and harmful to the environment.Fortunately,the recently developed aqueous solution processing is considered to be a safe and effective method for green oxide electronics.More compatible with the next generation of new FPD.Herewith we demonstrate a simple and ecofriendly water-induced approach to fabricate In2O3 based thin films.Since the large Lewis acid strength value,small radius,and high bonding strength with oxygen are key parameters for dopants,we reduce the off-state current of the In2O3 device by incorporating elements such as P,Ni,B,etc.Meanwhile,the threshold voltage and stability are improved through the impurity mechanism.To further reduce the operating voltage of the device and improve the mobility of the device,we introduce a high-K dielectric material(Zr O2)to replace the traditional Si O2 gate insulating layer.The main contents are as follows:Firstly,the influence of P doping on the microstructure and the electron transport properties were investigated in detail.The structure of the thin film was unchanged by doping P,all the films were smooth and uniform with similar thickness.It was proved that the electrical performance and stability of the device were not affected by the surface quality and thickness of the film.The optical band gap of the film increases with P content,and the transmittance was pretty.The oxygen vacancy(VO)and interfacial defect state of the film decrease with the the proportion of P.P was an effective defect state inhibitor.Furthermore,the optimal solution-processed InPO TFTs exhibit high performance,including:?_sat=6.33 cm²/V s,Ion/Ioff=6.10×10⁶,S=0.60V/dec,and VTH=2.97 V.Secondly,the effect of various ratios of Ni on In2O3 films were explored.Ni acted as a practical role,including:(1)The crystallinity of In2O3 was improved;(2)The transmittance and optical band gap of films were increased;(3)Reduce the VO content of the film.Meanwhile,the on/off current ratio of the devices were decresed,and the threshold voltage was shift forward;(4)Improve positive bias stability(PGBS)and negative bias stability(NGBS)for devices;(5)The carrier concentration was decreased,and Ni element had the large Lewis acid value(L),small ionic radius,the binding dissociation energy strength was stronger compared to In.Thus,the mobility will not drop significantly after Ni doping.Thirdly,In BO TFTs with different proportions of B were prepared and studied.Among these,B played a crtical role in reducing the VO and improving the transmittance of the films.In addition,the structure,surface quality and uniformity of the films were not changed with the B increased.Moreover,the addition of B was beneficial to the reduction of the off-state current of the In2O3 device,the threshold voltage of devices shift to the positive direction.The optimal B doping concentration was 10 mol%,including:?_sat=8.23 cm²/V s,Ion/Ioff=2.84×10⁶,VTH=4.78 V,S=0.65V/dec.However,the doping ratio of B was approximately 15 mol%,the performance of device starts to deteriorate owing to the defect formation via incomplete dehydration of excess B(OH)3.On the basis of the best device,we replaced the traditional Si O2dielectric layer with the solution-processed Zr O2 thin film,which further reduced the operating voltage of the In BO TFT by 10%and save the power consumption of the device.It was observed that the performance of the device was improved due to the high capacitance per unit area of the high-K material,including:?_sat=11.0 cm²/V s,Ion/Ioff=7.98×10⁴,S=0.19 V/dec,and VTH=0.09 V.