US Patent 11335725 High efficiency wide spectrum sensor

A method for fabricating an optical sensor includes: forming, over a substrate, a first material layer comprising a first alloy of germanium and silicon having a first germanium composition; forming, over the first material layer, a graded material layer comprising germanium and silicon; and forming, over the graded material layer, a second material layer comprising a second alloy of germanium and silicon having a second germanium composition. The first germanium composition is lower than the second germanium composition and a germanium composition of the graded material layer is between the first germanium composition and the second germanium composition and varies along a direction perpendicular to the substrate.