Simulation And Optimization Of Double Active Layer Heterostructure A-IZO/IGZO TFT

At present,according to the rapid development of technology,traditional materials such as amorphous silicon have been unable to meet the high demand of display due to its poor transmittance of light and low mobility.indium.Amorphous indium-gallium-zinc(a-igzo)material is the new product under the development of display technology development.Compared with the traditional amorphous silicon,the amorphous indium gallium zinc oxide has the characteristics of good mobility,good uniformity,high light transmittance in the visible light range,large area preparation by low temperature process on the flexible substrate and so on.These advantages make a-IGZO TFT a promising product for sensors,flexible electronics,and high-resolution flat-panel displays.However,with the disadvantages for unstable of a-IGZO material,it can not be put into large-scale production and application.To solve this problem,the researchers proposed a double active layer structure of amorphous oxide a-IZO/IGZO TFT.Considering that a-IZO and a-IGZO have the same type of conduction,both of which are n-type,and have different electron affinity and band gap,the heterojunction structure will be formed after they contact.The simulation software SILVACO TCAD is used to simulate and optimize the performance of double active layer a-IZO/IGZO with heterojunction structure.The main work of this paper is divided into three parts.Firstly,the optical and electrical properties of the amorphous oxide thin film transistor are analyzed,and the conductive mechanism of a-IGZO TFT and the device simulation environment are introduced.Secondly,the ATLAS simulation module in SILVACO software was used to establish the device model and density of state model of a-IZO /IGZO TFT with heterojunction structure.The effects of maximum value of oxygen vacancy,standard deviation and average energy on the electrical properties of the device were studied by changing the parameters of the density of oxygen vacancy.Simulation results show that the device performance is optimal when the thickness ratio of active layer is 20:20.Changing density parameters of oxygen vacancy state of the front channel a-IZO has little effect on the device,while the parameter of a-IGZO DOS of oxygen vacancy is the key to change characteristics of the device.Finally,considering few researchers have discussed the influence of the interface state of active layer heterojunction on the device,the interface state model was established.The specific changes of a-IZO /IGZO TFT with or without interface state and the influence of interface DOS parameters on device characteristics were studied.It is found that the existence of the interface state will increase the threshold voltage and sub-threshold swing,reduce the performance of the device,and have the greatest impact on the device when the thickness of a-IZO is 5 nm.The performance of the device will be affected by density of interface conduction band tail state and slope of interface conduction band tail state.