BAND-STRUCTURE AND OPTICAL-TRANSITIONS OF STRAINED SI/GE SUPERLATTICES

Si/Ge strained superlattices grown along [001] direction appear in six different space groups. For Ge-strained superlattices grown on a [001] Si surface, the band structure, the symmetry labels at Γ point, as well as optical transition probabilities for five space groups have been calculated on the basis of a tight-binding model, including the spin-orbit coupling. A strong dependence of the energy gap and the optical transition probabilities on symmetry is found. These findings are discussed in terms of strain, folding and symmetry arguments. © 1990.