Glass-Like Heat Conduction in High-Mobility Crystalline Semiconductors

TL;DR

This paper reports that certain high-mobility crystalline semiconductors with a specific structure exhibit glass-like thermal conductivity due to dopant-ion dynamics causing strong phonon scattering, despite their crystalline nature.

Contribution

It demonstrates that dopant-ion interactions in Ge clathrates lead to glass-like thermal conductivity in high-mobility crystalline semiconductors, a novel insight into heat conduction mechanisms.

Findings

Ge clathrates show amorphous-like thermal conductivity

High electron mobility coexists with glass-like heat conduction

Dopant-ion dynamics cause strong phonon scattering

Abstract

The thermal conductivity of polycrystalline semiconductors with type-I clathrate hydrate crystal structure is reported. Ge clathrates (doped with Sr and/or Eu) exhibit lattice thermal conductivities typical of amorphous materials. Remarkably, this behavior occurs in spite of the well-defined crystalline structure and relatively high electron mobility ($\sim 100 cm^2/Vs$). The dynamics of dopant ions and their interaction with the polyhedral cages of the structure are a likely source of the strong phonon scattering.