Band offsets between SiO2 and phase change materials in the (GeTe) x (Sb2 Te3) 1-x pseudobinary system

Abstract

The energy band alignment between stoichiometric phase change alloys residing along the pseudobinary line of GeTe-Sb2 Te3 [(GeTe) x (Sbb2 Te3) 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 (Sb2 Te3) 1-x alloy, exhibiting a parabolic dependence on the amount of GeTe in the alloy. Increasing the proportion of GeTe in the (GeTe) x (Sb2 Te3) 1-x alloy was generally found to increase (decrease) the valence band (conduction band) offsets, while the binary alloys (GeTe, Sb2 Te3) have similar band offset values. This information could be useful for phase change memory device design and optimization. © 2011 American Institute of Physics.