Long mean free paths of roomerature THz acoustic phonons in a high thermal conductivity material

Ting Han Chou, Lucas Lindsay, Alexei A. Maznev, Jateen S. Gandhi, Donna W. Stokes, Rebecca L. Forrest, Abdelhak Bensaoula, Keith A. Nelson, Chi Kuang Sun

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23 Scopus citations

Abstract

We report measurements of roomerature mean free paths of long-lived THz acoustic phonons in wurtzite GaN. Longitudinal phonon wave packets are excited and probed by femtosecond laser pulses in two InGaN-GaN multiple quantum well structures separated by a GaN layer. By measuring the temperature dependence of the phonon attenuation in the range 80-300 K we isolate the intrinsic phonon mean free path at 300 K which is found to be 5.3 and 3.5 μm at 1.06 and 1.43 THz, respectively. The measurements are found to be in good agreement with ab initio calculations which show that the main channel of the acoustic phonon decay is a three-phonon scattering process involving the acoustic phonon and two high-frequency optical phonons. Our results indicate that the contribution of low-THz acoustic phonons to thermal transport in GaN is relatively smaller than in Si; thus finite size effects are expected to be less important in GaN.

Original languageEnglish
Article number094302
JournalPhysical Review B
Volume100
Issue number9
DOIs
StatePublished - Sep 4 2019

Funding

The contribution by T.-H.C. and C.-K.S. was supported by the Ministry of Science and Technology, Taiwan, through Grant No. MOST 106-2112-M-002-004-MY3. First-principles calculations were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The contribution by A.A.M. and K.A.N. was supported by the US Department of Energy, Office of Basic Energy Sciences under Award No. DE-FG02-00ER15087. The contribution by J.S.G., D.W.S., R.L.F., and A.B. was supported by the University of Houston Grants to Enhance Research Program (Grant No. 55322).

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