AMPLIFICATION OF HIGH-FREQUENCY ULTRASOUND IN A STRONG ELECTRIC FIELD.

The amplification of high-frequency ultrasound by a drift current of conduction electrons at high electric field strength that creates the drift is separated. It is shown that the electric field may effect the elementary events of emission and absorption of ultrasonic phonons by the electrons. As a result, the nonlinear effects accompanying the amplification of the sound can be suppressed to a significant degree. Moreover, the residual small nonlinearity does not decrease the sound amplification, but on the contrary, increases it.