Role of surface-segregation-driven intermixing on the thermal transport through planar Si/Ge superlattices

Peixuan Chen, N. A. Katcho, J. P. Feser, Wu Li, M. Glaser, O. G. Schmidt, David G. Cahill, N. Mingo, A. Rastelli

Research output: Contribution to journalArticle

Abstract

It has been highly debated whether the thermal conductivity κ of a disordered SiGe alloy can be lowered by redistributing its constituent species so as to form an ordered superlattice. By ab initio calculations backed by systematic experiments, we show that Ge segregation occurring during epitaxial growth can lead to κ values not only lower than the alloy's, but also lower than the perfect superlattice values. Thus we theoretically demonstrate that κ does not monotonically decrease as the Si- and Ge-rich regions become more sharply defined. Instead, an intermediate concentration profile is able to lower κ below both the alloy limit (total intermixing) and also the abrupt interface limit (zero intermixing). This unexpected result is attributed to the peculiar behavior of the phonon mean free path in realistic Si/Ge superlattices, which shows a crossover from abrupt-interface- to alloylike values at intermediate phonon frequencies of ∼3 THz. Our calculated κ's quantitatively agree with the measurements when the realistic, partially intermixed profiles produced by segregation are considered.

Original languageEnglish (US)
Article number115901
JournalPhysical review letters
Volume111
Issue number11
DOIs
StatePublished - Sep 9 2013

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Chen, P., Katcho, N. A., Feser, J. P., Li, W., Glaser, M., Schmidt, O. G., Cahill, D. G., Mingo, N., & Rastelli, A. (2013). Role of surface-segregation-driven intermixing on the thermal transport through planar Si/Ge superlattices. Physical review letters, 111(11), [115901]. https://doi.org/10.1103/PhysRevLett.111.115901