Thermal conductivity of crystalline AlN and the influence of atomic-scale defects

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 3. method, finding that it ranges from 674 +/- 56Wm(-1) K-1 at 100 K to 186 +/- 7 Wm(-1) K-1 at 400 K, with a value of 237 +/- 6Wm(-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 similar to 7 mu m at room temperature, and 50% by phonons with MFPs over similar to 0.3 mu m. Consequently, the effective thermal conductivity of AlN is strongly reduced in submicrometer thin films or devices due to phonon-boundary scattering. Published under license by AIP Publishing.