Resonant Raman Scattering by Raman-Active Infrared-Inactive Phonons in II-IV Semiconductors

The compounds in the family Mg₂X(X=Si, Ge, Sn, Pb) crystallize in the antifluorite structure and constitute small-gap semiconductors. We use Raman scattering techniques to investigate the surface light scattering of these materials. The frequencies of their long-wavelength optical phonons at 300 and 77 ^∘{}K are established. From these values we were able to determine the effective force constants of the modes and compare them with values found in the literature. Second-order scattering has also been examined. The most striking feature of these materials, in connection with the present work, is the resonant scattering that they all exhibit for excitation frequencies between 2.40 and 2.71 eV. The resonance is attributed to interband electronic transitions. Good agreement is found between the present experimental results and an existing theoretical model on resonant Raman scattering.