STUDY OF BULK AND SURFACE PHONONS AND PLASMONS IN GAAS/ALAS SUPERLATTICES BY FAR-IR AND RAMAN-SPECTROSCOPY

Measurements by Raman spectroscopy, oblique incidence far-IR power reflection spectroscopy and attenuated total reflection spectroscopy have been used to study bulk and surface phonons and plasmons in semiconductor superlattices and multiple quantum wells. Raman spectroscopy has been used to investigate the properties of confined optical phonons, and far-IR measurements have been used to investigate the dielectric response parallel and perpendicular to the layers. Measurements are presented on 2 + 2, 4 + 4 and 6 + 6 GaAs/AlAs superlattice specimens and on a GaAs/ Al0.35Ga0.65 As multiple quantum well. The far-IR spectra of all samples are in good agreement with spectra calculated from superlattice dielectric functions which take account of the optical response of the confined transverse and longitudinal optical modes, using phonon frequencies taken from the Raman spectra. © 1990.