Thermal conductivity of bulk and nanoscaled Si/Ge alloys from the Kinetic Collective Model

TL;DR

This paper investigates how phonon transport regimes in Si/Ge alloys influence thermal conductivity, revealing a transition from collective to kinetic behavior driven by impurity and boundary scattering effects.

Contribution

It introduces a model explaining the transition between collective and kinetic phonon transport regimes in Si/Ge alloys, accounting for size and impurity effects on thermal conductivity.

Findings

Pure silicon exhibits mainly collective phonon transport.

Impurities and boundaries suppress collective transport, reducing thermal conductivity.

The model explains rapid thermal conductivity decay at low impurity levels.

Abstract

Several hitherto unexplained features of thermal conductivity in group IV materials, such as the change in the slope as a function of sample size for pure vs. alloyed samples and the fast decay in thermal conductivity for low impurity concentration, are described in terms of a transition from a collective to kinetic regime in phonon transport. We show that thermal transport in pure bulk silicon samples is mainly collective, and that impurity/alloy and boundary scattering are responsible for the destruction of this regime with an associated strong reduction in thermal conductivity, leaving kinetic transport as the only one allowed when those resistive scattering mechanisms are dominant.