One illustrative photodetector disclosed herein includes an N-doped waveguide structure defined in a semiconductor material, the N-doped waveguide structure comprising a plurality of first fins, and a detector structure positioned on the N-doped waveguide structure, wherein a portion of the detector structure is positioned laterally between the plurality of first fins. In this example, the photodetector also includes at least one N-doped contact region positioned in the semiconductor material and a P-doped contact region positioned in the detector structure.