methods and structures for providing single - color or multi - color photo - detectors leveraging plasmon resonance for performance benefits . in one example , a radiation detector includes a semiconductor absorber layer having a first electrical conductivity type and an energy bandgap responsive to radiation in a first spectral region , a semiconductor collector layer coupled to the absorber layer and having a second electrical conductivity type , and a plasmonic resonator coupled to the collector layer and having a periodic structure including a plurality of features arranged in a regularly repeating pattern .