First-Principles Study On Sc-doped Ge₂Sb₂Te₅ Phase Change Materials

Phase change memory(PCM)has fast read or write capabilities,high storage density and good data retention,so it is considered to be one of the most promising next-generation nonvolatile memories;but its higher power consumption hinders its further development.As the core of phase change memory,phase change material plays an important role in reducing power consumption and improving the performance of phase change memory.Element doping and construction of phase change superlattice materials are effective ways to optimize the performance of phase change materials.This paper uses the first-principles calculation method to calculate the Sc-doped Ge₂Sb₂Te₅(GST)phase change material(SGST),analyzes the physical origin of the low power consumption during the RESET process,and explores the main factors affecting the band structure and the modulation effect of doping concentration and lattice strain on its crystalline electronic structure;In addition,we constructed a superlattice structure(GST)_m/(SGST)_n based on the Sc-doped GST and the pure GST primitive cell.Then we investigated the mechanical stability,and the influence of different interfaces and different components on its electronic structure.The results show that:(1)Compared with GST,SGST has wider band gap and larger carrier effective mass,leading to the decrease of carrier mobility and the increase of resistivity,which is the main reason for the reduction of power consumption;(2)The bond length change between atoms is the main factor affecting the energy band structure.Compared with the Sb-Te bond,the Te-Te bond has a greater impact on the band structure of GST;(3)With the increase of doping concentration,the band gap value of SGST gradually increases.When the doping concentration reaches 20%,the band gap value basically remains unchanged;With the increase of tensile strain,the band gap decreases;with the increase of compressive strain,the band gap increases first and then decreases.When the compression strain is 1%,the band gap reaches the maximum;compared with the tensile strain,the band gap of SGST system changes more obviously under the compression strain;(4)In the(GST)_m/(SGST)_n superlattices at different interfaces,there are 10 structures that exhibit semiconductor characteristics.Their band gaps are in the range of 0.08-0.63e V,and they have good mechanical stability.In addition,in Sb/Te1interface superlattices with different compositions,changing the composition of GST has a more obvious modulation effect on the band gap.