Xu, R.L., Rojo, M.M., Islam, S.M., Sood, A., Vareskic, B., Katre, A., Mingo, N., Goodson, K.E., Xing, H.G., Jena, D., Pop, E., 2019, “Thermal Conductivity of Crystalline AlN and the Influence of Atomic-Scale Defects,” Journal of Applied Physics, Vol. 126, 185105.

Abstract

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Aluminum nitride (AlN) plays a key role in modern power electronics and deep-ultraviolet photonics, where an understanding of its thermal properties is essential. Here, we measure the thermal conductivity of crystalline AlN by the 3ω method, finding that it ranges from
674 ± 56 Wm−1 K−1 at 100 K to 186 ± 7Wm−1 K−1 at 400 K, with a value of 237 ± 6 Wm−1 K−1 at room temperature. We compare these data with analytical models and first-principles calculations, taking into account atomic-scale defects (O, Si, C impurities, and Al vacancies).  We find that Al vacancies play the greatest role in reducing thermal conductivity because of the largest mass-difference scattering. Modeling also reveals that 10% of heat conduction is contributed by phonons with long mean free paths (MFPs), over ∼7 μm at room temperature, and 50% by phonons with MFPs over ∼0.3 μm. Consequently, the effective thermal conductivity of AlN is strongly reduced in submicrometer thin films or devices due to phonon-boundary scatterin