Electronic properties of (Si)₁₂/(Ge)₄and (Si)₁₆/(Ge)₄superlattices grown on Si(001): theoretical results

The energy band structure (nature of the bandgap, optical transitions) for the strained (Si)12/(Ge)4 and (Si)16/(Ge)4 superlattices grown on a Si(001) substrate is presented. The calculations predict that these materials are almost direct--gap semiconductors, but with very small transition probabilities across the direct gap. These findings are discussed in connection with experimental data.