High thermal conductivity materials show promise for thermal mitigation and heat removal in devices. However, shrinking the length scales of these materials often leads to significant reductions in thermal conductivities, thus invalidating their applicability to functional devices. In this work, we report on high in-plane thermal conductivities of 3.05, 3.75, and 6 μm thick aluminum nitride (AlN) films measured via steady-state thermoreflectance. At room temperature, the AlN films possess an in-plane thermal conductivity of ∼260 ± 40 W m–1 K–1, one of the highest reported to date for any thin film material of equivalent thickness. At low temperatures, the in-plane thermal conductivities of the AlN films surpass even those of diamond thin films. Phonon–phonon scattering drives the in-plane thermal transport of these AlN thin films, leading to an increase in thermal conductivity as temperature decreases. This is opposite of what is observed in traditional high thermal conductivity thin films, where boundaries and defects that arise from film growth cause a thermal conductivity reduction with decreasing temperature. This study provides insight into the interplay among boundary, defect, and phonon–phonon scattering that drives the high in-plane thermal conductivity of the AlN thin films and demonstrates that these AlN films are promising materials for heat spreaders in electronic devices.
Digital Object Identifier (DOI)
Published in ACS Nano, Volume 15, Issue 6, 2021, pages 9588-9599.
© 2021 American Chemical Society
High In-Plane Thermal Conductivity of Aluminum Nitride Thin Films by Md Shafkat Bin Hoque, Yee Rui Koh, Jeffrey L. Braun, Abdullah Mamun, Zeyu Liu, Kenny Huynh, Michael E. Liao, Kamal Hussain, Zhe Cheng, Eric R. Hoglund, David H. Olson, John A. Tomko, Kiumars Aryana, Roisul Galib, John T. Gaskins, Mirza Mohammad Mahbube Elahi, Zayd C. Leseman, James M. Howe, Tengfei Luo, Samuel Graham, Mark S. Goorsky, Asif Khan, and Patrick E. Hopkins is licensed under a Creative Commons CC BY-NC-ND 4.0 license.
Hoque, M. S., Koh, Y. R., Braun, J. L., Mamun, A., Liu, Z., Huynh, K., Liao, M. E., Hussain, K., Cheng, Z., Hoglund, E. R., Olson, D. H., Tomko, J. A., Aryana, K., Galib, R., Gaskins, J. T., Elahi, M. M., Leseman, Z. C., Howe, J. M., Luo, T., … Hopkins, P. E. (2021). High in-plane thermal conductivity of aluminum nitride thin films. ACS Nano, 15(6), 9588–9599. https://doi.org/10.1021/acsnano.0c09915