RESONANT BRILLOUIN-SCATTERING IN GAP NEAR THE INDIRECT ABSORPTION-EDGE

Resonant Brillouin scattering in GaP by the transverse acoustic phonons has been studied at room temperature in the region of the indirect absorption edge by making use of an acoustic-domain injection method. The spectral dependences of the Brillouin-scattering cross sections have shown a monotonic decrease (resonant cancellation) as the incident-photon energy extends beyond the indirect-gap energy. The experimental dispersion curves have been well interpreted by a theoretical model of the indirect-gap resonance and an additional dielectric theory of the direct-gap resonance. The spectral dependences of the photoelastic constants, |p11 - p12| and |p44|, have also been determined as a by-product of the Brillouin-scattering data. © 1979.