Optical phonon modulation in semiconductors by surface acoustic waves

TL;DR

This study demonstrates that surface acoustic waves can modulate optical phonons in semiconductors, affecting Raman scattering intensity and phonon energies, with potential for phonon control at micrometer scales.

Contribution

It provides experimental evidence and theoretical understanding of optical phonon modulation by SAWs in semiconductors, highlighting local and non-local effects.

Findings

SAWs induce ~10^{-3} change in Raman intensity

Modulation primarily due to optical phonon energy shifts

Activation of optical modes with large wave vectors

Abstract

We investigate the modulation of optical phonons in semiconductor crystal by surface acoustic wave (SAW) propagating on the crystal surface. The SAW fields induce changes on the order of 10\textsuperscript{-3} in the average Raman scattering intensity by optical phonons in Si and GaN crystals. The SAW-induced modifications in the Raman cross-section are dominated by the modulation of the optical phonon energy by the SAW strain field. In addition to this local contribution, the experiments give evidence for a weaker and non-local contribution arising from the spatial variation of the SAW strain field. The latter is attributed to the activation of optical modes with large wave vectors and, therefore, lower energies. The experimental results, which are well described by theoretical models for the two contributions, prove that optical phonons can be manipulated by SAWs with $\mu$m wavelengths