Optical phonon modulation in semiconductors by surface acoustic waves

摘要

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