Thermal Boundary Conductance Across Heteroepitaxial ZnO/GaN Interfaces: Assessment of the Phonon Gas Model

John T. Gaskins, George Kotsonis, Ashutosh Giri, Shenghong Ju, Andrew Rohskopf, Yekan Wang, Tingyu Bai, Edward Sachet, Christopher T. Shelton, Zeyu Liu, Zhe Cheng, Brian M. Foley, Samuel Graham, Tengfei Luo, Asegun Henry, Mark S. Goorsky, Junichiro Shiomi, Jon Paul Maria, Patrick E. Hopkins

Research output: Contribution to journalArticlepeer-review

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We present experimental measurements of the thermal boundary conductance (TBC) from 78-500 K across isolated heteroepitaxially grown ZnO films on GaN substrates. This data provides an assessment of the underlying assumptions driving phonon gas-based models, such as the diffuse mismatch model (DMM), and atomistic Green's function (AGF) formalisms used to predict TBC. Our measurements, when compared to previous experimental data, suggest that TBC can be influenced by long wavelength, zone center modes in a material on one side of the interface as opposed to the '"vibrational mismatch"' concept assumed in the DMM; this disagreement is pronounced at high temperatures. At room temperature, we measure the ZnO/GaN TBC as 490[+150,-110] MW m-2 K-1. The disagreement among the DMM and AGF, and the experimental data at elevated temperatures, suggests a non-negligible contribution from other types of modes that are not accounted for in the fundamental assumptions of these harmonic based formalisms, which may rely on anharmonicity. Given the high quality of these ZnO/GaN interfaces, these results provide an invaluable, critical, and quantitative assessment of the accuracy of assumptions in the current state of the art computational approaches used to predict phonon TBC across interfaces.

Original languageEnglish (US)
Pages (from-to)7469-7477
Number of pages9
JournalNano letters
Issue number12
StatePublished - Dec 12 2018

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering


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