Damping of electron-hole-droplet motion. I. Deformation potential scattering

We report on a study of the damping of electron-hole-droplet (EHD) motion due to scattering by acoustical phonons coupled by the deformation-potential mechanism. Screening by the electrons and holes is taken into account in the random-phase approximation. Numerical results are presented for Ge in the low-velocity limit, EHD velocities less than the sound velocity, and high-velocity limit, velocities greater than the sound velocity. The low-velocity results are found to be in good agreement with the values of the phonon damping measured by an ultrasonic-absorption experiment. The results suggest that in recent measurements of EHD motion one must take into account driving forces produced by, perhaps, a phonon wind. In the high-velocity case the damping is found to be sufficiently large to make it unlikely that velocities greater than the sound velocity will be observed experimentally.