Phonon heat conduction in Al_1-xSc_xN thin films

Aluminum scandium nitride (Al_1-xSc_xN) is regarded as a promising material for high-performance acoustic devices used in wireless communication systems. Phonon scattering and heat conduction processes govern the energy dissipation in acoustic resonators, ultimately determining their performance quality. This work reports on phonon scattering processes and thermal conductivity in Al_1-xSc_xN alloys grown by molecular beam epitaxy with the Sc content (x) up to 0.26. The thermal conductivity shows a descending trend with increasing Sc content. Temperature-dependent measurements show an increase in thermal conductivity as the temperature increases at temperatures below 200 K, followed by a plateau at higher temperatures (T > 200 K). Application of an analytical Debye-Callaway model allows us to estimate the effects of boundary and alloy scattering on the observed thermal conductivity behavior. This work provides insight for phonon scattering mechanisms and the resultant thermal conductivity in Al_1-xSc_xN, paving the way for future investigation of materials and design of acoustic devices.