Experimental study of phonon-folding in SI/Ge and Si/SiGe structures designed for thermoelectric applications

摘要

We rreport data of Raman study of si/Ge and Si/SiGe superlattices designed for thermoelectric applications. The obtained Raman spectra clearly indicate the presence of folded doublets from longitudinal acoustic phonons. Due to the significant difference in the sound velocities for Si and Ge the position of the doublets strongly depends on the superlattice layer thickness and ordering. Comparison of the Raman data or different samples with measured thermal and thermoelectric properties allows us to determine a samples with measured thermal and thermoelectric properties allows us to determine a correlation between the strength of the phonon configement in these structures and their termoelectric properties. Our experimental results are consistent with recent theoretical prediction of increased thermoelectric figure of merit in semiconductor quantum wells.