Measurement of Miniband Electronic Structure in Ordered Ge- Si Atomic Layer Superlattices Using Electro-Reflectance Spectroscopy

Electro-reflectance spectroscopy has been used to identify the formation of minibands resulting from the superlattice-induced formation of a Kronig-Penney like superlattice whose period is similar to that of the unit cell dimension. Using this technique, we can show that a superlattice consisting of alternating single monolayers has a period too short for a mini-zone to be created. Minizones are first seen in structures containing alternate bi-layers of Si and Ge, and for a 4 monolayer by 4 monolayer superlattice, the minizone properties are well described by parameters of bulk Si and bulk Ge bandstructures.'