Structure and optical properties of strained Ge-Si superlattices grown on (001) Ge

Ge-Si strained-layer superlattices have been synthesized on (001) Ge with unit-cell periodicity of ten atomic monolayers along the growth direction. Microstructural characterization establishes extended planar superlattice layering. X-ray diffraction is used to measure the superlattice composition. Optical reflectance spectra show new optical transitions at energies theoretically predicted for superlattice-induced direct optical transitions at the center of the Brillouin zone.