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实验表明,硒(Se)掺杂可以大幅提高锗碲(Ge Te)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Ge Te微观结构和电学性质的影响机制尚不清楚。本文采用第一性原理计算方法,对Se掺杂Ge Te相变材料的几何构型、成键性质和电子性质进行了理论研究。结果表明,对于理想Ge Te晶体,掺杂的Se原子优先取代Te原子。而对含本征Ge空位的Ge Te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Ge Te两晶相的体积差异。计算结果为解释实验中硒掺杂导致的奇特相变性质提供了重要线索。
Experiments show that selenium (Se) doping can significantly improve the recrystallization temperature of Ge Te phase-change materials, which leads to higher service temperatures and better data retention. However, The mechanism of the influence of the microstructure and the electrical properties is not clear. In this paper, the geometrical configuration, bonding properties and electronic properties of the Ge-doped Ge Te phase-change material have been studied theoretically by the first-principles calculation method. The results show that, for the ideal Ge Te crystal, the doped Se atoms preferentially replace the Te atoms. For Ge Te systems with intrinsic Ge vacancies, Se tends to replace Te atoms nearest to Ge vacancies. Se atoms and Ge vacancies have attracted the role of inhibiting the movement of Ge vacancies, thereby increasing the recrystallization temperature. Se doping results in the volume shrinkage of the rhombic phase containing Ge vacancies and the decrease of the bandgap, while the volume fraction of the face centered cubic phase containing Ge vacancies expands. Se doping reduces the volume difference of the Ge Te two-phase phase. The calculated results provide important clues to explain the peculiar phase transitions caused by selenium doping in the experiment.