Ellipsometry and Raman spectroscopy of MBE-grown undoped Si-Si0.78Ge0.22/(001)Si superlattices

Abstract

Spectroscopic ellipsometry and Raman spectroscopy have ben sued to characterize Si/Si0.78Ge0.22 superlattices grown by molecular beam epitaxy at different substrate temperatures, 550 degrees C < Ts < 810 degrees C. The result are interpreted to give information on material and interface quality, layer thicknesses, and state of strain, and are in good agreement with XRD, SIMS and RBS investigations. The observed frequencies of zone-folded longitudinal acoustic phonons in a high quality sample agree well with those calculated using Rytov's theory of acoustic vibrations in layered media.