Patent ID: 8741684

Claim:
A method comprising: providing a planarized silicon-based photonics substrate comprising a silicon waveguide structure; depositing a dielectric layer over the planarized silicon-based photonics substrate; selectively etching the dielectric layer, thereby exposing at least a portion of the silicon waveguide structure; selectively etching the exposed portion of the silicon waveguide structure to form a step-like template; using the silicon waveguide structure as a seed layer to selectively grow in the step-like template a germanium layer that extends above the dielectric layer; and planarizing the germanium layer to form a planarized germanium layer, wherein the planarized germanium layer does not extend above the dielectric layer and, as a result of the step-like template, has an inverted rib shape, wherein the inverted rib shape comprises a lower portion and an upper portion that is wider than the lower portion, wherein the lower portion comprises an optically-active region, and wherein the upper portion comprises laterally-overhanging portions that extend laterally above and beyond either side of the optically active region lower portion.