Band offsets between SiO2 and phase change materials in the (GeTe)x(Sb2Te3)1−x pseudobinary system

The energy band alignment between stoichiometric phase change alloys residing along the pseudobinary line of GeTe–Sb2Te3[(GeTe)x(Sb2Te3)1−x] and SiO2 was obtained employing high-resolution x-ray photoelectron spectroscopy. The valence band offsets were determined using both the core-level spectra and valence band spectra in the analysis. The results obtained show that the band offsets vary with the composition of the (GeTe)x(Sb2Te3)1−x alloy, exhibiting a parabolic dependence on the amount of GeTe in the alloy. Increasing the proportion of GeTe in the (GeTe)x(Sb2Te3)1−x alloy was generally found to increase (decrease) the valence band (conduction band) offsets, while the binary alloys (GeTe, Sb2Te3) have similar band offset values. This information could be useful for phase change memory device design and optimization.