NONLINEAR EFFECTS IN THE ABSORPTION OF ULTRASOUND OF INTERMEDIATE FREQUENCY IN SEMICONDUCTORS.

Nonlinear effects in the absorption of ultrasound are studied assuming that the wavelength of the ultrasound is much shorter than the diffusion length but much longer than the mean free path of carriers. The nonlinear effects are due to the heating of carriers by the electric field of an acoustic wave. It is shown that, for some scattering mechanisms such that the momentum relaxation time is a rapidly increasing function of the energy, the absorption coefficient of sound can be very sensitive to the heating by the acoustic wave. The nonlinear absorption coefficient can differ considerably from the linear coefficient even for weak heating parameters. The dependences of the nonlinear absorption coefficient of sound on the intensity and frequency of the acoustic wave are studied under the outlined conditions.