Impact of Nitrogen on the Crystallization and Microstructure of Ge-Rich GeSbTe Alloys

The influence of N concentration on the crystallization kinetics, microstructural evolution, and composition of Ge-rich GeSbTe (GGST) alloys during thermal annealing, using X-ray diffraction and scanning and transmission electron microscopy is reported. It is shown that the incorporation of N in GGST tends to slow down the phase separation, crystallization, and growth processes during annealing. This can be attributed to the reduced diffusivity of Ge, which interacts and quickly bonds with N. Technological advantages of N doping are also discussed, considering the increased stability of the amorphous phase with respect to its parent crystalline phase, finer microstructure, flatness of the GeSbTe (GST) films after crystallization, and disappearance of the low-resistivity hexagonal phase at high temperature.