Origin of the reverse optical-contrast change of Ga-Sb phase-change materials—An ab initio molecular-dynamics study

A large number of phase-change materials (PCMs) have been developed experimentally; however, only Ge2Sb2Te5-based PCMs have been significantly explored using ab initio molecular-dynamics (AIMD) simulations. We present an AIMD study of the full melt/quench/anneal PC cycle for Ga-Sb materials, namely, the stoichiometric composition, GaSb, and the near-eutectic alloy, Ga16Sb84. The calculated electronic densities of states and optical reflectivities are compared between the amorphous and crystalline phases for both compositions, and it is shown that the contrasting opto-electronic properties of each crystalline material can be attributed to different structural transformations of Ga and Sb on crystallization from the amorphous state