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.
Universal phonon mean free path spectra in crystalline semiconductors at high temperature
Freedman, J. P., Leach, J. H., Preble, E. A., Sitar, Z., Davis, R. F., & Malen, J. A. (2013). Universal phonon mean free path spectra in crystalline semiconductors at high temperature. Scientific Reports, 3, . https://doi.org/10.1038/srep02963