Bandstructure Near Misfit Dislocations in Si Quantum Wells

High electron mobility structures have been built for several years now using strained silicon layers grown on SixGe(I.x) with x in the 25-40% range. In these structures, a thin layer of silicon is grown between layers of unstrained GeSi alloy. Matching of the two lattices in the plane of growth produces a bi-axial strain in the silicon, splitting the conduction band and providing light electron levels for enhanced mobility. If the silicon channel becomes too thick, strain relaxation can occur by injection of misfit dislocations at the growth interface between the silicon and GeSi alloy.12 The strain field of these dislocations then gives rise to a local potential variation that limits electron mobility in the strained Si channel. This study seeks to verify this mechanism by measuring the absolute conduction band shifts which track the local potential near the misfit dislocations.