In some embodiments, a semiconductor device is provided. The semiconductor device includes an epitaxial structure having a group IV chemical element disposed in a semiconductor substrate, where the epitaxial structure extends into the semiconductor substrate from a first side of the semiconductor substrate. A photodetector is at least partially arranged in the epitaxial structure. A first capping structure having a first capping structure chemical element that is different than the first group IV chemical element covers the epitaxial structure on the first side of the semiconductor substrate. A second capping structure is arranged between the first capping structure and the epitaxial structure, where the second capping structure includes the group IV chemical element and the first capping structure chemical element.