Optical properties of strained GeSi superlattices grown on (001)Ge

Abstract

Modulation spectroscopy has been used to study optical transitions in GeSi strained layer superlattices with unit cell periodicity of ten atomic monolayers in the growth direction. The samples in this report were grown on (001)Ge producing a 4.5% compressive strain along the superlattice growth direction. Spectra taken at 40 K show additional sharp structures near 0.94 eV comparable in magnitude with that measured for bona fide direct optical transitions in bulk germanium. These results are discussed in terms of structurally induced optical transitions in GeSi-ordered superlattices and are compared with recent theoretical and experimental results on similar structures.