NOVELTY - The detector has a voltage biasing element applying bias voltage to a matrix material such that electrical current is directly generated in an electromagnetic radiation (EMR) absorption region based on a cooperative plasmon effect in the region when EMR in visible to near infrared wavelength range is incident upon the region. A charge multiplication region is arranged relative to the region to avalanche multiply the current generated in the region. A nanoparticle absorber array comprises a set of detector elements, where each detector element comprises respective groups of nanoparticles.    USE - Multi-spectral avalanche photodiode (APD) electro-magnetic radiation (EMR) detector i.e. solar cell (claimed), for visible to near infrared wavelength used in an application e.g. single photon counting experiments, telecommunication and imaging, in the lowest light level environment e.g. heavily over cast starlight at night. Can also be used for focal plane array detector.    ADVANTAGE - The detector utilizes natural unipolar nature of the electrical properties when employing nano-plasmonics together with a Schottky barrier, thus allowing nano-plasmonic structures to provide ultra-low thermal conductivity (k) values for providing very high photo-level detection performance even at room temperature. The detector eliminates the need for cooling, thus reducing weight and power consumption. The detector utilizes nanoparticle absorber arrays for improving performance of the detector.    DETAILED DESCRIPTION - A dominant mechanism of the detector for decays in a cooperative plasmon effect is non-radiative. The detector comprises detection circuitry (1870) i.e. silicon complementary metal-oxide-Semiconductor (Si-CMOS) circuitry. The matrix material comprises group IV, group II-VI, and group III-V semiconductor material.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a multi-spectral ADP EMR detector with a stacked detector layer.    Pixels of APD detector (1810a, 1810b)    APD detector layers (1820, 1830, 1840, 1850)    Top insulation region (1854)    Bottom insulation region (1856)    Detection circuitry (1870)