Explicating the phase evolution in As and Se co-doped Ge2Sb2Te5 films for phase change memory

In this work, the structural, electrical, electro-thermal, and switching properties of As₂Se₃-doped Ge₂Sb₂Te₅ films have been studied. Upon annealing, the films undergo a phase transition at higher temperatures from the amorphous state to a stable hexagonal phase via a metastable face-centered-cubic phase, notably without any observed phase separation and lattice distortion. Doping with As₂Se₃ significantly improves the thermal stability of the amorphous phase, increasing the crystallization temperature from ⁓168 °C to ⁓225 °C (x = 0.21). The band gap is increased due to the formation of high-energetic Ge-Se and As-Se bonds. Furthermore, the data retention temperature for a 10-year period is substantially improved from 78 °C to 124.93 °C with a corresponding increase in the activation energy. The threshold current required for phase transformation is reduced to 0.23 mA. Higher-doped films generate more Joule heat due to their increased resistivity, which, in turn, allows for a reduction in power consumption for the same applied current, indicating promising applications in phase change memory devices.