Thermal stability and microstructure of germanium antimony telluride thin films under interdiffusion conditions

Abstract

This paper investigates the interdiffusion behaviors of alloy components of the Ge–Sb–Te system and its influence on the thermal and electrical instability of Ge–Sb–Te alloy films. When SbxTe1−x/Ge bilayer films are annealed at 400 °C, the Ge–Sb–Te intermediate layers are formed at the interface between SbxTe1−x and Ge. This is caused by the interdiffusion of Ge, Sb, and Te. The highest degree of interdiffusion is observed in the Ge–Te system, while the existence of Sb retards the interdiffusion of Ge and Te in the SbxTe1−x/Ge bilayer films. The outdiffusion and sublimation of low-melting-point Sb and Te occur at the annealing temperature of 500 °C, which leads to the instability of the Ge–Sb–Te intermediate layers. The phase-change memory (PCM) device employing a Ge2Sb2Te5 intermediate layer exhibit stable endurance, because of the robustness of Ge2Sb2Te5 compound with respect to the phase separation during the repetitive set–reset cycles.