title: Universal phonon mean free path spectra in crystalline semiconductors at high temperature.
abstract: Thermal conductivity in non-metallic crystalline materials results from cumulative contributions of phonons that have a broad range of mean free paths. Here we use high frequency surface temperature modulation that generates non-diffusive phonon transport to probe the phonon mean free path spectra of GaAs, GaN, AlN, and 4H-SiC at temperatures near 80 K, 150 K, 300 K, and 400 K. We find that phonons with MFPs greater than 230 ± 120 nm, 1000 ± 200 nm, 2500 ± 800 nm, and 4200 ± 850 nm contribute 50% of the bulk thermal conductivity of GaAs, GaN, AlN, and 4H-SiC near room temperature. By non-dimensionalizing the data based on Umklapp scattering rates of phonons, we identified a universal phonon mean free path spectrum in small unit cell crystalline semiconductors at high temperature.
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA, USA 15213.
authors.forename: Justin P
authors.initials: JP
authors.lastname: Freedman
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Leach
authors.forename: Edward A
authors.initials: EA
authors.lastname: Preble
authors.forename: Zlatko
authors.initials: Z
authors.lastname: Sitar
authors.forename: Robert F
authors.initials: RF
authors.lastname: Davis
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Malen