The Study On Rare Earth Praseodymium Doped Oxide Thin Film Transistor

Metal oxide thin film transistors(MOTFTs)have excellent characteristics such as high mobility,good uniformity,and low off-state current.They have shown great promise in the field of new display,but the poor negative bias voltage stability under illumination and temperature(NBITS)conditions is a crucial issue that MOTFTs must be resolved before their commercialization into optoelectronic devices.In our previous research,it was found that the IZO TFTs with Pr doping exhibited a remarkable enhancement in negative gate bias stress under illumination.To further explore the doping characteristics of Pr,the rare earth element Pr have been doped into indium gallium oxide(IGO)in this paper,and a high NBITS stability TFT based on the etch-stopper layer(ESL)structure has been prepared.In addition,a self-aligned coplanar structure device based on PrIGO as the active layer have been developed.The specific results are as follows:This article first explores the preparation conditions of the IGO active layer,and obtaines process parameters with relatively good basic performance.Then,the different proportions of Pr element are doped into IGO thin film by co-sputtering method,and a remarkable enhancement in NBITS stability is achieved in the PrIGO TFTs.Finally,to explore the reasons for the improved stability of PrIGO TFTs,the IGO thin films before and after Pr doping are characterized and analyzed.To further explore the mechanism for the improvement of NBITS stability,the low-frequency noise characteristics of IGO TFTs and PrIGO TFTs have been studied.According to the low frequency noise characterization and analysis results,the correspondence of the normalized drain current noise power spectral density(S_ID/I²_DS)and frequency shows 1/f^?(??0.8)low frequency noise behavior for IGO TFTs and PrIGO TFTs.The low-frequency noise mainly comes from the channel region,which conforms to the carrier number fluctuation model for IGO TFTs and PrIGO TFTs.Based on the carrier number fluctuation model,the defect state density is extracted to be 8.12×10¹⁷ cm^-3·e V^-1 and 9.73×10¹⁷ cm^-3·e V^-1 for IGO TFTs and PrIGO TFTs,respectively.It is confirmed that the doping of Pr into the IGO system can induce shallow-level defect states,and the trap-assisted model is still applicable in the IGO system,and the improvement of NBITS stability can be attributed to the trap-assisted model.Finally,the self-aligned coplanar structure device based on PrIGO as the active layer has been developed,and the experimental process of preparing the self-aligned coplanar structure device is explored.The results show that when the N₂O plasma processing power is 40 W,the active layer thickness is 20 nm and the oxygen content in the sputtering atmosphere is 10%,the device has relatively good basic performance.The saturation mobility(?_sat)of the device is 26.9cm²/Vs,the turn-on voltage is-0.4 V,the sub-threshold swing(SS)is 0.26 V/decade,and the current-on-off ratio is greater than 10⁹.