Title: Superdiffusive heat conduction in semiconductor alloys. II. Truncated Lévy formalism for experimental analysis

Abstract

Nearly all experimental observations of quasiballistic heat flow are interpreted using Fourier theory with modified thermal conductivity. Detailed Boltzmann transport equation (BTE) analysis, yet, reveals that the quasi-ballistic motion of thermal energy in semiconductor alloys is no longer Brownian but instead exhibits Lévy dynamics with fractal dimension α < 2 . In this work, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure Lévy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any “effective” thermal parameters and without any a priori knowledge of microscopic phonon scattering mechanisms. Identified α values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal Lévy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.

Authors:

Vermeersch, Bjorn ^[1]; Mohammed, Amr M. S. ^[1]; Pernot, Gilles ^[2]; Koh, Yee Rui ^[1]; Shakouri, Ali ^[1]

---

+ Show Author Affiliations

1. Purdue Univ., West Lafayette, IN (United States)
2. Univ. of Bordeaux (France)

Publication Date:

Tue Feb 10 00:00:00 EST 2015

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Center for Energy Efficient Materials (CEEM)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1369779

Alternate Identifier(s):

OSTI ID: 1179940

Grant/Contract Number:  

SC0001009

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B, Condensed Matter and Materials Physics

Additional Journal Information:

Journal Volume: 91; Journal Issue: 8; Related Information: CEEM partners with the University of California, Santa Barbara (lead); Purdue University; Los Alamos National Laboratory; National Renewable Energy Laboratory; Journal ID: ISSN 1098-0121

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE