Thermal Conductivity of Crystalline AlN and the Influence of Atomic-Scale Defects

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.

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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 scattering.

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