硒掺杂锗碲相变存储材料的第一性原理研究

摘要

硒(Se)掺杂可以大幅提高锗碲(GeTe)相变存储材料的再结晶温度,使其具有更高的服役温度和更好的数据保持力,然而Se掺杂对GeTe微观结构和电学性质的影响机制尚不清楚.采用第一性原理计算方法,对Se掺杂GeTe相变存储材料的几何构型、成键性质和电子性质进行了理论研究.结果表明,对于GeTe完美晶体,掺杂的Se原子优先取代Te原子.而对含本征Ge空位的GeTe体系,Se倾向于取代与Ge空位最近邻的Te原子.Se原子与Ge空位具有吸引作用,抑制了Ge空位的移动,从而提高其再结晶温度.Se掺杂导致含Ge空位的菱方相体积收缩,带隙减小,而使含Ge空位的面心立方相体积膨胀,带隙增大.Se掺杂减小了GeTe两晶相的体积差异.计算结果为解释实验中Se掺杂导致的奇特相变性质提供了重要线索.%Doping Se can significantly improve the recrystallization temperature of GeTe phase-change material according to recent experiments,endowing GeTe with a higher working temperature and better data re-tention.However,the impact of Se on the structure and electrical properties of GeTe is not clear.In this pa-per,we investigated the effect of Se on the microstructure,bonding characters and electrical properties of crys-talline GeTe using first-principles calculation.The results show that the doping Se atom prefers to replace Te in ideal GeTe,while for GeTe systems with intrinsic Ge vacancies,Se tends to replace the Te atoms which are the nearest neighbors of Ge vacancy.The attraction between Se atom and Ge vacancies hinders the movement of Ge vacancies,and thus increases the recrystallization temperature.Furthermore,a shrink of lattice volume and a small reduction of band gap are found in rhombohedral GeTe with Ge vacancies through doping Se, while in face-centered cubic GeTe with Ge vacancies,Se doping causes an expansion in lattice volume and an increase in band gap.Doping Se reduces the volume discrepancy between the two crystalline phases.The cal-culation results provide clues for explaining the unique phase transformation phenomena of Se doped phase-change materials.