Effect of dopants on the structure and properties of Ge2Sb2Te5 studied by Ab initio calculations

Ge2Sb2Te5 is technologically important for phase-change random access memory applications. In this work, the effect of doping Ag, Cd, In and Sn on the structure and chemical bonding of Ge2Sb2Te5 has been studied by ab initio calculations. It has been shown that the 3.7 at.% dopants drastically weaken the Te–Te bond strength in the–Te–(vacancy)–Te–configuration while maintaining its rocksalt symmetry. According to the analysis of formation energy, doping at the Ge site of Ge2Sb2Te5 phase is more favourable. The doped Ge2Sb2Te5 phases demonstrate either semiconductor or metallic behavior, which is attributed to the valence electrons of the dopants that mainly contribute to either the conductivity or chemical bonding.