Tensile strain mapping in flat germanium membranes

Abstract

The membranes have the potential to be excellent growth and integration platforms: compared to bulk Ge epitaxially grown on Si (001) they are perfectly flat and XRD and PV-TEM confirm the misfit dislocation network has been removed. The strain profile across the membrane is symmetrical and the membrane is slightly more tensile strained than the bulk material. The difference in strain across the membrane is too small to create a large variation in optical device performance across the entire membrane. Coupled with the smoother surface and absence of misfit dislocation network compared to the bulk material, the membranes are both excellent strain tuning platforms for optical applications and, more generally, for growth of subsequent active layers.