Notes on Reproducibility of Ge2Sb2Te5 Properties

Sputtered Ge2Sb2Te5 (GST) films are utilized in phase-change devices, whereas the quantitative reproducibility of fundamental properties such as refractive index and electrical conductivity remains unsatisfactory. Herein, it is exemplified that the properties are considerably affected by sputter conditions. It seems that high-quality amorphous films are deposited with slow dc sputtering at high voltages and low Ar pressures. It is also discussed whether the cubic GST is a degenerate or a nondegenerate semiconductor.