STRAIN AND PIEZOELECTRIC EFFECTS ON THE PHONON FREQUENCIES IN HETEROSTRUCTURES

It is shown that the strain characterization of heterostructures based on phonon frequency shifts is modified when piezoelectric fields are present. The well-known phenomenological theory and Raman practice for obtaining the strain phonon deformation potentials, i.e., parameters connecting frequency shifts with strains, are extended to include electric-field phonon deformation potentials. Both sets of deformation potentials can be obtained from combined Raman experiments under hydrostatic pressure, performed on strained layers grown along [001], [110], and [111]. Expressions are given for the frequency shifts in terms of the deformation potentials, for all scattering configurations allowed by selection rules.