Ultrasonic loss and gain mechanisms in semiconductors

Several kinds of interactions of ultrasound in semiconductors are reviewed. The subjects discussed are the effects of interaction with 1) thermal phonons, which produce temperature dependent attenuation; 2) free carriers, which may give attenuation or amplification; 3) electrons bound to shallow donors, giving rise to attenuation at low temperatures; and 4) other ultrasonic waves, which may give attenuation or amplification. An introduction to relaxation effects is included.