Brillouin Scattering Studies of Acoustoelectric-After-Effect in Semiconducting CdS

Acoustoelectric-after-effect followed by the abrupt termination of the externally applied voltage was studied in semiconducting CdS with Brillouin scattering measurements. Damping behaviors of the generated acoustic flux was first revealed experimentally. The acoustic loss is separated into electronic and nonelectronic contribution via linear and nonlinear process. The nonelectronic linear loss of the acoustic shear waves obeys ω 1.5 -law rather than Akhieser's prediction: ∝ω 2 . White's gain curve reduced by this non-electronic loss agrees well with our experimental results. Nonlinear acoustic loss via second harmonic generation was also estimated. The nonlinear loss is mainly ascribed to the nonlinear acoustoelectric interactions, but not to the lattice anharmonicity. Finally, the relationship between the acoustic flux φ and the acoustoelectric-after-current I was found to be I ∝φ 2 . This means that our observed after-current is mainly caused by the nonlinear acoustoelectric interactions.