Studying For The Selector Device Based On Polycrystal Line ZnO Material

Today,with the growing development of information storage technology,memory is one of the most important and fundamental components in the modern integrated circuit industry.The high integration,large storage capacity,high read/write speed and low power consumption of memory make it an important driving force for the development of the integrated circuit industry.The various types of memory on the market have formed a situation of blooming.After the flash memory has gone to the physical limit of technology,the revolutionary new non-volatile memory has dominated the entire storage industry.Representative non-volatile memories are mainly ferroelectric memories,magnetic memories,phase change memories,and resistive memories.Non-volatile memory mainly stores data in a cross-point array structure.In a highly integrated storage array,crosstalk problems and power consumption problems between units have not been effectively solved.The non-linear selectors are connected in series in the memory cell to avoid crosstalk and current leakage between the highly integrated memory arrays,and thus the research on the selector has received extensive attention.In recent years,research on selector is in full swing,and different working mechanisms and selectors of different structures have been studied by researchers.The practicability of these selectors is also controversial,and it is necessary to work with the memory in the crosspoint array to verify the reliability of the performance.Nonlinearity is one of the most important parameters that determine the performance of a selector device.Currently,there are mainly selector devices based on the phase change mechanism and the tunneling mechanism on the market.The main structures of the selector are MIM,MSI,NPN,NIPIN and MIEC structures.This paper mainly studies the selector which generates nonlinearity based on the tunneling mechanism,and improves the storage performance and the integration degree in the 1S1R structure.In this paper,the reliability of polycrystalline ZnO as a selector material is studied by a first-principles calculation method based on density functional theory.First,it is found through calculation that the electrical properties of different surfaces of ZnO crystals are different,and the cause of this phenomenon is the anisotropy of crystals.Secondly,by comparing the electrical properties and volt-ampere characteristic curves of the three different polymorphic models built,it is found that the grain boundary barrier is introduced in the polycrystalline state.The grain boundary barrier is the main reason for its nonlinearity,and its height determines the nonlinearity and conductivity.The strength of nonlinearity determines the rectification effect of RRAM devices.The higher nonlinearity of the selector can effectively solve the problem of crosstalk leakage of RRAM.In order to make the polycrystalline ZnO selector better match the operating current of the RRAM device,we doped the N element in the polycrystalline ZnO.The bandgap of the polycrystalline system is reduced to increase the conductivity of the device.In addition,considering the device structure on the process,we insert different electrodes at both ends of the polycrystalline ZnO,so that it can maintain excellent nonlinearity and conductivity under practical working conditions.We studied the electronic properties of C/polycrystalline ZnO/C,Cu/polycrystalline ZnO/Cu,Zn/polycrystalline ZnO/Zn under different electrode conditions.The insertion of the graphene electrode introduces an interface state and an interface barrier,and the presence of the interface barrier makes the nonlinear enhancement but the operating current is correspondingly reduced The Cu electrode also introduces an interface barrier,which is eliminated by adding H passivation.Due to the Cu potential away from the interface is higher than the average potential of ZnO,so that the electrode affects carrier transport.However,The Zn metal potential is almost equal to the ZnO potential,therefore the interface barrier is completely eliminated after H passivation.In addition,inserting the electrode can move the Fermi level up,resulting in an increase in the operating current of the system.Finally,the Zn/polycrystalline ZnO/Zn system can effectively solve the leakage and power consumption of RRAM.