This paper addresses the effect of generation of confined LO phonons by drifting electrons in quantum wells. We have obtained a general formula for the phonon increment as a function of the phonon wave vector, the electron drift velocity, and parameters of the structure. The kinetic parameters of the drifting electrons are estimated by using momentum and energy balance equations for electron scattering by the confined optical phonons. We have performed numerical estimates of the phonon increment, as well as the phonon lifetimes, and found that AlAs/GaAs/AlAs and GaSb/InSb/GaSb quantum well structures with high drift velocities can demonstrate the effect of generation of the coherent confined optical modes. Essentially, the phonon increment has a maximum as a function of the wave vector. This implies a strong selection of the generated phonon modes. We briefly discuss the nonlinear electron mechanism which stabilizes the increase of the phonon populations and provides for the steady-state phonon generation.

• Received 9 November 2000

DOI:https://doi.org/10.1103/PhysRevB.63.165308