Acoustic and Optical Phonon Frequencies and Acoustic Phonon Velocities in Silicon-Doped Aluminum Nitride Thin Films

TL;DR

This study measures how silicon doping affects phonon frequencies and velocities in AlN thin films, providing insights for optimizing high-power semiconductor devices.

Contribution

It offers new experimental data on phonon behavior in Si-doped AlN films using Brillouin-Mandelstam and Raman spectroscopy.

Findings

Optical phonon frequencies vary non-monotonically with Si doping.

Acoustic phonon velocity decreases by ~300 m/s at high doping levels.

Results can help optimize thermal management in high-power devices.

Abstract

We report the results of the study of the acoustic and optical phonons in Si-doped AlN thin films grown by metalorganic chemical vapor deposition on sapphire substrates. The Brillouin - Mandelstam and Raman light scattering spectroscopies were used to measure the acoustic and optical phonon frequencies close to the Brillouin zone center. The optical phonon frequencies reveal non-monotonic changes, reflective of the variations in the thin-film strain and dislocation densities with the addition of Si dopant atoms. The acoustic phonon velocity decreases monotonically with increasing Si dopant concentration, reducing by ~300 m/s at the doping level of 3 x 10^19 1/cm3. Knowledge of the acoustic phonon velocities can be used to optimize ultra-wide bandgap semiconductor heterostructures and minimize the thermal boundary resistance of high-power devices.