Preparation And Electrical Characterization Of InZnO:N Thin Film Transistors

Transparent thin Film Transistors (TFTs) are widely used in flat panel displays, but along with the improvement of requirements of display device size and performance, the silicon-based TFTs can’t meet the demands of application in industry. The major reason is that the mobility of amorphous silicon TFT is too low (less than 1 cm2/Vs), poly silicon TFT suffer from non-uniformity against large-area preparation and it is sensitive to visible light. Recently, the metal oxide thin film transistor represented by ZnO has been attracted more and more attention and research to solve these problems because of their advantages such as high optical transparency in the visible light region and higher field-effect mobility. However, the ZnO-TFT still has some defects due to the existence of Vo and Zni, the mobility is not high enough and the performance is not stable. In this dissertation, to solve the problems, InZnO:N-TFTs were fabricated and the electrical properties of the TFTs were improved by optimize the preparation condition. The details are as follows:The effect of InZnO:N films’thickness on the optical properties of the films was investigated. The results indicated that the transistor with an 30 nm thick InZnO:N exhibited the best performance with a field effect mobility of 37.1 cm2/Vs, a threshold voltage of -9.1 V, and an on/off ratio of 2.4E+07;The influence of annealing temperature on the performance of InZnO:N-TFTs has been studied, the results showed that annealing can improve the quality of the film, and the transistor annealed at 950℃ exhibited the best performance, with a threshold voltage of -9.1 V, a field effect mobility of 37.1 cm2/Vs, an on/off ratio of 2.4 E+07The effect of the oxygen contents in the preparation of active layer is investigated. We found that appropriate O2/Ar gas flow ratio is very beneficial for the InZnO:N TFTs, and when the O2/Ar gas flow ratio at 1/30, the transistor exhibited a high field-effect mobility of 39.3 cm2/Vs, a threshold voltage of 2.4 V and an on/off ratio of 1.1E+7.The influence of W/L and L on the performance of TFTs was also discussed. It was found that with the decrease of W/L, the performance of device degradation; and the performance of device improvement with the decrease of the L.