Phonon Transmission in AlN Interfaces with Varying Lattice Mismatch.

Efficient thermal management is becoming increasingly crucial in the design of electronic devices, particularly as they scale down to the nanoscale, where surface and interface effects dominate heat transfer. Ultra-wide bandgap semiconductors, such as AlN, are promising materials for high-power electronics, which demand high thermal conductivities to prevent overheating and maintain device performance. In these systems, thermal boundary resistance becomes a critical parameter, yet its accurate modeling remains challenging due to limited data on phonon transmission probabilities across interfaces. In this study, we utilized picosecond acoustics to investigate phonon transmission at interfaces of AlN and substrates with varying degrees of lattice mismatch. Counterintuitively, we found that interfaces with greater lattice mismatch exhibited enhanced phonon transmission compared to more ordered interfaces. These findings provide new insights into the intricate relationship between atomic disorder and thermal transport at nanoscale interfaces, offering potential pathways for optimizing heat dissipation in next-generation electronic devices.