Sign of the Raman tensor of diamond and zinc-blende-type semiconductors

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Abstract
Measurements of the scattering cross section give the magnitude, but not the sign of the Raman tensor. This sign is, however, uniquely obtained in calculations based on either microscopic theories or macroscopic bond polarizability models. We show that the sign of the Raman tensor can be found from experiments in which its scattering interferes with another scattering mechanism whose Raman tensor has a known sign. Thus, from interference between phonon scattering and inter-valence-band electronic scattering the phonon Raman tensor is found to be negative for silicon. A similar conclusion is reached for the Raman tensor of the TO phonon in GaAs from the interference with the effect of the macroscopic electric field in scattering by LO phonons.