Amplification of transverse acoustic phonons in quantum well heterostructures with piezoelectric interaction

We have analyzed amplification of transverse phonons confined in quantum we ll (QW) heterostructures through piezoelectric electron-phonon interaction with drifting electrons. It was found that this mechanism of interaction co uples the low-dimensional electrons and the shear-horizontal (SH) confined phonons. We have studied the electrostatic potential accompanying the SH wa ves and found that efficient interaction can be achieved for the lowest ant isymmetric SH phonon branch in a narrow band of phonon frequencies. For AlG aAs QWs the amplification coefficient was calculated to be on the order of 100 cm(-1) in the sub-THz phonon frequency range. These results suggest an electrical method for coherent phonon generation in the technologically wel l-developed AlGaAs QW heterostructures. (C) 2001 American Institute of Phys ics.