OPTICAL STUDY OF MBE GROWN UNDOPED SI-SI1-XGEX SI SUPERLATTICES/

Raman spectroscopy and spectroscopic ellipsometry have been used to ch aracterize Si/Si-0.78 Ge-0.22 superlattices grown by molecular beam ep itaxy on (001)Si at different substrate temperatures. The results are interpreted to give information on material and interface quality, lay er thicknesses, and state of strain. The observed frequencies of zone- folded longitudinal acoustic phonons in a high quality sample agree we ll with those calculated using Rytov's theory of acoustic vibrations i n layered media.