The Preparation And Characteristics Analysis Of Zinc Oxide Thin Film Transistors

As the main components of transistor liquid crystal display device and organic electroluminescent display device,thin film transistor has been hot researched.Since amorphous silicon thin film transistor with low cost has many shortcomings,Oxide thin film transistor as the replacement of amorphous silicon thin film transistors(TFTs)has been widely research in all world right now.However,Oxide thin film transistor is still exist many problems,so it is very important to improve the performance of the oxide thin film transistor.First of all,ZnO thin films have been deposited on the silica glass using magnetron sputtering,and using atomic force microscope(AFM)to observe the surface morphology of ZnO thin films,approximate polycrystalline surface morphology has been observed;ZnO thin film structure has been analyzed using X-ray diffraction method,the growth of ZnO thin film had good C axis orientation.Double beam UV-visible spectrophotometer has also been used to test absorption spectrum and transmittance of the ZnO thin films in the range of 320nm-900nm,in the visible light range ZnO thin film light transmittance was as high as above 85%;it could prove that ZnO thin films are transparent in visible range.And we have used the steps tester to test the thickness of the ZnO thin films,measured ZnO thin film thickness of 400 nm which was prepared under the condition of substrate heated to350?using RF magnetron sputtering 1.5 hours,lay a foundation for subsequent experiment and analysis.Thin-film diodes of Al/ZnO/Ni structure have been prepared with different thicknesses of Al electrode,analyzed the characteristics of rectifier.And thin film transistors with sandwich structure of Al/ZnO/Ni/ZnO/Al also have been prepared,which Al and Ni as a metal electrode,ZnO as the active layer.A Schottky contact was formatted between Ni and ZnO,and between Al and ZnO,there were two cases appeared:Schottky contact and Ohmic contact.Using semiconductor analysis tester measured the diode and thin film transistor we prepared.From the measuring results,we can know that the operating current of the device prepared can reach mA level,it means that it is suitable for application.And through the diode measuring results,the Al/ZnO contact in the case of different Al film thicknesses were not the same.When Al film thickness was 20nm,the contact was mainly embodied in the ohmic contact;when the Al film thickness is 40 nm,the contact was mainly embodied in the Schottky contact,and at this time,the Al/ZnO/Ni structure formed quantum well structures similarly,constituted a kind of artificial superlattice film diode,measuring results showed that under the condition of positive and negative bias the diode has the characteristics of conduction..Through the calculation of measuring results of ZnO thin film transistors,basic electrical parameters of the ZnO thin film transistor were got:transistors transconductance,output resistance,voltage amplification factor,carrier mobility,and so on;the carrier mobility value was 0.3018cm~2/Vs,the threshold voltage was0.5V.