Si/CaF2 superlattices: a direct gap structure due to interface state coupling

One promising approach for the development of silicon-based light-emitting devices is the epitaxial growth of Si nanostructures. In this context, the lattice matched system CaF2/Si/CaF2 as prototype of a well controlled and ordered Si-based system with known microscopic structure is proposed. For this system, a new mechanism is found leading to a direct band gap based on the coupling of interface states in very thin Si layers.