First-principles study of Se doped GeTe phase-change material

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 retention. However, the impact of Se on the structure and electrical properties of GeTe is not clear. In this paper, we investigated the effect of Se on the microstructure, bonding characters and electrical properties of crystalline 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 calculation results provide clues for explaining the unique phase transformation phenomena of Se doped phase-change materials.