The Effects Of Grain Orientation And Grain Boundary On The Electrical Behaviors Of FeFET: A Phase Field Simulation

The ferroelectric field effect transistor?FeFET?memory is considered to be the one of the most promising next-generation memory because of its low power consumption,high read and write speed,nonvolatile,antiradiation,high integration and non-destructive readout.As the core of FeFET memory,the property of ferroelectric thin film determines the working stability of ferroelectric memory.Compared with single crystal ferroelectric thin films,polycrystalline ferroelectric thin films are easier to prepare and more widely used in experiments and practical applications.So,it is important to study the simulation of polycrystalline ferroelectric thin film and the research to electrical properties of polycrystalline ferroelectric thin film.Firstly,the grain orientation distribution and grain boundary thickness have a certain influence on the ferroelectric properties of polycrystalline ferroelectric thin films,which will have an important effect on the electrical properties of polycrystalline ferroelectric thin films.Secondly,there is a built-in electric field at the polycrystalline ferroelectric thin film which caused by the accumulated charges at the grain boundary,which will affect the properties of polycrystalline ferroelectric thin films.In this paper,the effects of grain orientation and grain boundary on the electrical properties of FeFET with polycrystalline BaTiO3 ferroelectric thin film were studied by using the basic device equation of the Metal/Oxide/Semiconductor?MOS?field effect transistor combining with the phase field method.:?1?The phase field model of polycrystalline ferroelectric thin films was established.The influence of grain orientation distribution and grain boundary thickness on the ferroelectric properties of polycrystalline ferroelectric thin films were investigated.The results show that the remanent polarization and the coercive field decreases in the BaTiO3 polycrystalline ferroelectric thin films with random grain orientation distribution.With the increase of grain boundary thickness,the remanent polarization gradually reduces.?2?The charge accumulation at the grain boundary was considered,and the effect of the accumulated charges on the ferroelectric properties of the polycrystalline ferroelectric thin films was studied.The results show that a built-in electric field formed due to the the accumulated charges at the grain boundary and it exert the large influence on the the domain structure and domain switching of the BaTiO3 thin film.With the increase of the strength of the charge accumulation,the remnant polarization and the coercive field decrease.?3?The effect of grain orientation,grain boundary thickness and charge accumulation at the grain boundary on the electrical properties of FeFET are studied.The results are as follows.The random distribution of grain orientation will leads to a decrease in the remanent polarization,the memory window and the open mode I_ds of the FeFET,and a rise in the closed mode I_ds of the FeFET.With the increase of grain boundary thickness,the remanent polarization of the FeFET,the memory window and the open mode I_ds decreases and the closed mode I_ds increases.With the increase of the strength of the charge accumulation at the grain boundary,the remnant polarization of the FeFET,the memory window and the open mode I_ds decreases and the closed mode I_ds increases gradually.