Preparation And Electrical Properties Of Indium-based Oxide Semiconductor Thin Film Transistors

Since the 21st century,thin film transistors are widely used in the wearable and flexible electronics,flat panel display,andtheresolution and size of the display device are determined by its characteristics.In the market,the amorphous silicon TFT has low mobility,low stability and high photosensitivity,the polycrystalline silicon TFT due to the complex fabrication craft and high cost,which restricted the application of thin film transistor.Metal oxides had become the mainstream material of thin film transistor channel layer,since metal oxides have excellent electric properties,high transparency,large area integration and other advantages.In₂O₃ has attributed much attention because of its wide band gap,optical transparency and high filed effect carrier mobility.In this paper,bottom-gate thin film transistors with an indium base film as the channel layer were fabricated on SiO₂/Si by sol-gel process andits properties were studied.The main work accomplished includes the following:?1?The In₂O₃ thin films transistors were deposited on SiO₂/Si by sol-gel process.The film structure,morphology,optical and electrical properties were studied.FromtheXRDpattern,itisobserved thatIn₂O₃crystal has preferred growth orientation?222?.The transmittance of In₂O₃film approach 90%in the visible region and the optical bandgap is Eg=3.54eV.Furthermore,In₂O₃-TFT fabricated at 300?showed higher mobility(2cm²V^-1s^-1),higher threshold voltage(V_Th=-18V),higher subthreshold swing?SS=10V/dec?and lower on/off current ratio(I_on/I_off=6×10²).?2?The IZrO and IAO thin films were deposited on SiO₂/Si by sol-gel process.the influence of zirconium doping on the structure,optical and electrical properties of IZrO TFT was studied.All the IZrO films showed a crystalline structure,in the visible region average transmittance of all the films was over90%.When the zirconium concentration is 7%,optimal electrical properties of IZrO TFT was obtained(I_on/I_off=3.84×10⁴,V_Th=-4V,?=0.02cm²V^-1s^-1).The IAO TFT was deposited on SiO₂/Si by sol-gel processed.the effects of the aluminum doping,active layers thickness on the electrical properties of TFT were studied,respectively.when the aluminum is 5%,the channel thickness 24nm,the IAO thin film as active layers has a optimized performance I_on/I_off=2×10⁵,V_Th=0V,?=0.09cm²V^-1s^-1.The channel layers were exposed to ultraviolet-ozone assisted thermal annealing.The optical UV-ozone treatment time?25 min?,the IAO TFT with optimal electrical properties of IAO TFT obtained,such as V_Th=-1.5V,?=0.05m²V^-1s^-1,I_on/I_off=2×10⁵,?V_Th=1.2V,SS=0.25V/dec.?3?The IAO/In₂O₃ bilayer thin film were deposited on SiO₂/Si by sol-gel process.The electrical performance of IAO/In₂O₃ bilayer TFTs was systematically investigated and compared with TFT using single In₂O₃ or IAO channel layers.It was found that the electron mobility of bilayer TFT(?=1.1 cm²V^-1s^-1)are great large than those of IAO TFT(?=0.02 cm²V^-1s^-1).More importantly,the positive bias stability?PBS?of the bilayer TFTs(?V_Th=3.1V)was significantly enhance compared to single In₂O₃ TFT(?V_Th=6V).The thickness depended performance and stability of the front In₂O₃ layer was examined experimentally.The optimum device was achieved for the 6 nm thick In₂O₃ device,which exhibited a high performance,such as?=1.2cm²V^-1s^-1,I_on/I_off=1.13×10⁴,?V_Th=3.9V.