| Flat panel display products have been developing in the direction of large size,full high definition,thinness and flexibility.The oxide thin-film transistors(TFTs)have absorbed much research attention as potential candidates and gradually replaced the conventional amorphous and polycrystalline silicon TFTs in transparent displays,especially in the active matrix display applications,due to the advantages including high mobility,excellent uniformity,good transparency,low processing temperature and good process compatibility.In recent years,n-channel oxide TFTs have exhibited high device performances and been used in commercial display application.However,the high-performance p-channel oxide TFTs have been rarely reported due to the lack of the p-type oxide semiconductors with high intrinsic hole mobility.As a result,the current use of transparent oxide TFTs is mostly limited to unipolar devices based on ntype semiconductors.This work focused on the research of high-performance SnOx TFTs.By using low-temperature plasma channel processing technique,the bipolar conduction property was achieved in the SnOx and the n-/p-channel SnOx TFTs with high performances were fabricated.The stability upon illumination of the SnOx TFTs was also studied.In addition,the effect of the plasma channel processing on the SnOx TFT device performances was further investigated using the experiments and TCAD simulation tool.Through this work,significant and substantial progress has been made in the following aspects:(1)Using the oxygen plasma channel processing with the optimal processing time,the n-channel SnOx TFT device was successfully demonstrated with high field-effect mobility(87.6 cm2V-1s-1)and low operation voltage(5 V).The device performance improvements could be ascribed to the optimal oxygen plasma treatment that reduced the amount of Sn2+ phase and formed the oxygen-rich n-type SnOx,resulting in high carrier concentration.Besides,the n-channel SnOx TFT device exhibited high stability upon illumination with visible light.(2)Using the aluminum(Al)doping in the SnOx active channel layer,the p-type Al-doped SnO TFT device was successfully demonstrated with high field-effect mobility(8 cm2V-1s-1)and low operation voltage(3 V).These good performances could be attributed to the substitution reactions of Al3+-Sn4+,which increased the hole carrier concentration in the channel layer.The device characteristics including the on/off current ratio and subthreshold swing were further improved by the fluorine plasma treatment on the channel,which passivated the trap states and significantly reduced the acceptor-like traps.(3)The effect of the plasma channel processing on the n-/p-channel SnOx TFT device performances was studied by introducing the density of states(DOS)model in the TCAD device simulation.These simulation results provide theoretical basis for the further optimization of the TFT device performances.In this work,high-performance n-/p-channel SnOx TFTs were successfully demonstrated based on the bipolar conduction property of the SnOx material.The present results are of great importance for realizing full oxide semiconductor CMOS,which provide an important reference for new generation display technology and Internet of Things application. |
