Here, we report an optical absorption redshift map for GeTe-Sb2Te3 pseudo-binary alloys. We
found that, with phase change from amorphous to crystalline, the observed redshift increases with
Ge concentration along pseudo-line of compositions, which directly reflects the enhanced electron
delocalization/resonant bonding and increased carrier concentrations in the respective crystal
compounds. The measured valence band maximum shift towards the Fermi energy from
amorphous to crystalline phase supports the observed similar trend in redshift and carrier density.
We show that the correlation between optical redshift and carrier density, attributed to the resonant
bonding, can be rationalized by calculating the valence electron concentration, the ionicity, and
hybridization.
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Copyright (2013) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Appl. Phys. 114, 123504 (2013) and may be found at http://dx.doi.org/10.1063/1.4822311.