EFFECT OF ORDERING, INTERFACE IMPERFECTIONS AND CLUSTERS, AND EXTERNAL ELECTRIC-FIELDS ON OPTICAL-SPECTRA OF SI-SIGE HETEROSTRUCTURES

A microscopic theory of optical transitions in Si-SiGe heterostructure s which offers a direct comparison of the strength of the optical tran sitions in ordered and disordered structures is presented herein, and suggests a new enhancement mechanism via localization at interface imp erfections and Ge islands, and shows that even ultrashort period Si-Ge superlattices exhibit a strong red Stark shift in place of the expect ed blueshift familiar from analogous GaAs-AlAs systems.