Role of Surface-Segregation-Driven Intermixing on the Thermal Transport through PlanarSi/GeSuperlattices

• DOI: 10.1103/physrevlett.111.115901
• Publication Date: 2013-09-09T16:58:13Z
• Authors: Peixuan Chen; N. A. Katcho; J. P. Feser; Wu Li; M. Glaser; O. G. Schmidt; David G. Cahill; N. Mingo; A. Rastelli
• Keywords: 02 engineering and technology; 0210 nano-technology

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 systematic experiments, we show that Ge segregation occurring during epitaxial growth lead values not only lower than alloy's, but also perfect superlattice values. Thus theoretically demonstrate does monotonically decrease Si- and Ge-rich regions become more sharply defined. Instead, intermediate concentration profile is able below both limit (total intermixing) abrupt interface (zero intermixing). This unexpected result attributed peculiar behavior phonon mean free path in realistic Si/Ge superlattices, which shows crossover from abrupt-interface- alloylike at frequencies ∼3 THz. Our calculated κ's quantitatively agree with measurements when realistic, partially intermixed profiles produced are considered.