Phonon attenuation in heavily doped many-valley semiconductors. II. the effect of mass anisotropy

For pt.I see ibid., vol.15, p.6991 (1982). The authors have derived the phonon relaxation rate for anisotropic mass cases in heavily doped many-valley semiconductors by solving the equations of motion for the single-particle density matrices within the self-consistent field and the relaxation time approximations. Explicit expressions have been given for longitudinal and transverse waves propagating along the principal directions in Ge and Si. Numerical calculations have been performed for n-type Ge at T=0K. The following have been found. The effect of the mass anisotropy is remarkable in the high-frequency region, while in the low-frequency region it becomes negligibly small. There exist two cut-off wavenumbers in the electron-phonon interaction for the (110) and (111) longitudinal mode is qualitatively the same as in the isotropic mass case. A discussion of the recent work on phonon absorption due to the electron-hole liquid (EHL) in Ge by Dietsche et al. (1982) is also given.