Resonant Brillouin Scattering in GaSe and GaS

Abstract

Resonant Brillouin scattering in the layer-type semiconductors GaSe and GaS by the pure-transverse phonons has been investigated at room temperature by using the amplified acoustical-domain injection method. The measured spectral dependence of the Brillouin-scattering cross sections has shown a weak resonant cancellation for both GaSe and GaS in the region of the fundamental absorption edges. The data have shown a good agreement with the theoretical analyses based on the quasistatic approximation and Loudon’s light-scattering theory. The resonant cancellation has been successfully interpreted by taking into account the lowest-direct-gap (direct-exciton) resonance process for GaSe and lowest-indirect-gap resonance process for GaS. These analyses have also indicated that the nonresonant electronic transition is dominant in the Brillouin-scattering process even in the region near the fundamental absorption edge.