Phonon transport across a Si–Ge interface: The role of inelastic bulk scattering

Jesse Maassen,Vahid Askarpour

doi:10.1063/1.5051538

Abstract

Understanding phonon transport across heterojunctions is important to achieve a wide range of thermal transport properties. Using the McKelvey-Shockley flux method with first-principles modeling, we theoretically investigate the phonon transport properties of a Si–Ge interface with a focus on the role of inelastic bulk phonon processes. We observe significant inelastic scattering near the interface that redistributes the heat among the phonons as a result of non-equilibrium effects driven by the junction. These effects are most pronounced when the length of the junction is comparable to the average phonon mean-free-path. What controls these inelastic processes is elucidated.

Highlights

Interfacial phonon transport has been investigated using molecular dynamics (MD),4–21 atomistic Green’s function (AGF),22–26 and the Boltzmann transport equation (BTE).27–29 Each approach has its advantages and has been used to identify various phonon transport processes across heterojunctions
AGF and MD naturally treat the interfacial phonon properties, which lead to non-bulk interface modes that have been proposed to mediate phonon transport
We investigate a Si–Ge interface focusing on the role and origin of inelastic bulk scattering in Si scitation.org/journal/apm and Ge, using the McKelvey-Shockley flux method combined with density functional theory (DFT) and an ideal interface model

Summary

Introduction

Interfacial phonon transport has been investigated using molecular dynamics (MD),4–21 atomistic Green’s function (AGF),22–26 and the Boltzmann transport equation (BTE).27–29 Each approach has its advantages and has been used to identify various phonon transport processes across heterojunctions. The BTE showed that inelastic bulk scattering can result in non-trivial temperature and heat current distributions near an interface.28 This may be a general feature of heterojunctions, but what exactly controls such inelastic processes and how this affects phonon transport have yet to be fully understood.

Results

Conclusion