EFFECT OF PHONON-SCATTERING ON FREE-CARRIER ABSORPTION IN N-TYPE INDIUM-ANTIMONIDE FILMS

The free-carrier absorption in n-type InSb films has been investigated for carriers confined in quasi-two-dimensional (2D) semiconductors wi th the nonparabolic energy band of electrons. We discuss the effect of phonon scattering on the free-carrier absorption coefficient (alpha) for both deformation-potential coupling and piezoelectric coupling. al pha is found to depend on the photon polarization relative to the dire ction normal to the quasi-2D structure, the photon frequency, the film thickness, and the temperature. alpha could be complex due to the int eraction between photons, phonons, and electrons. (i) When the acousti c phonon scattering is dominant, alpha increases with decreasing the f ilm thickness for phonons polarized parallel or perpendicular to the l ayer plane. It is also shown that alpha increases with decreasing phot on frequency and increasing temperature for photons polarized parallel to the layer plane, while for photons polarized perpendicular to the layer plane the alpha temperature-dependence is more complicated. (ii) If the piezoelectric scattering is dominant, alpha is also decreasing with increasing the film thickness for photons polarized parallel or perpendicular to the layer plane. But alpha decreases with increasing temperature for photons polarized perpendicular to the layer plane. Mo reover, numerical results for the parallel polarization are much small er than those for the perpendicular polarization.