Abstract
Using Brillouin-scattering techniques, the geometrical and spectral evolution of the acoustic flux is studied amplified from the background noise in n-type GaAs under the influence of an external electric field. Measurements are performed in oxygen-doped material over the temperature range 190-240K which corresponds to a resistivity range of about 30 to 2 Omega cm. The growth of the acoustic flux can be distinctly separated into a linear and a nonlinear regime. Some of the results are discussed in terms of some recent theories of parametric processes in the acoustoelectric effect. The validity of the phenomenological current-controlled model is also discussed. The evolution of the flux at high resistivities for long voltage pulses has been studied.