Acoustic properties of heavily doped many-valley semiconductors in the weak-localization regime

Abstract

We have derived expressions for the ultrasonic attenuation coefficient α and the sound-velocity change Δv of heavily doped many-valley semiconductors at low frequencies in the weak-localization regime where any intervalley scattering strength has been taken into account. Quantum corrections due to the effect of localization give a negative contribution to α and Δv and are insensitive to temperature provided that the intervalley scattering time is independent of temperature, while those due to the effect of mutual interaction give a positive contribution to α and Δv and decrease with increasing temperature. The whole behavior of δα and δΔv, the deviations from classical form for the attenuation coefficient and the sound-velocity change, are determined by the competition between the effects of localization and the effects of mutual interaction mentioned above. The magnitude of δα and δΔv increase with decreasing intervalley scattering strength. For comparison, expressions for α and Δv in heavily doped single-valley semiconductors have also been derived. The sign of the quantum corrections to α and Δv is the same as that to the electrical conductivity in the many-valley case but opposite in the single-valley case.