AMPLIFICATION OF ACOUSTIC-WAVES DUE TO AN EXTERNAL TEMPERATURE-GRADIENT IN SUPERLATTICES

Amplification of short-wave sound propagating along the axis of a semiconductor superlattice by electrons of the lowest miniband in an external temperature gradient is investigated theoretically. The mechanism of absorption of phonons is due to Landau damping. Unlike a homogeneous material, the threshold field at which absorption turns over to amplification depends on the superlattice parameters and the wavelength of the sound wave.