A photo detector comprising a grating (PC). The grating (PC) is arranged on top of a surface of an active semiconductor layer. The grating (PC) is patterned in uninterrupted first strips (ST1), that are arranged in a first direction (x) in a first predetermined interval (a), and second strips (ST2), that are arranged in a second direction (y) in a second predetermined interval (b). The second strips (ST2) each comprise at least one interruption in a region between each two neighboring first strips (ST1) in form of a predetermined gap (d). Positively doped regions (P) and negatively doped regions (N) each are arranged as strips in parallel with the first strips (ST1) such that in a region between each two neighboring first strips (ST1) alternately either one of the positively doped regions (P) or one of the negatively doped regions (N) is arranged.