Abstract: A photodetector comprises a semiconductor substrate having an input surface for receiving illumination, control electrodes for control of photogenerated charge within the substrate and a filter on the radiation input surface of the substrate, the filter comprising a dielectric-metal band pass filter having a metal layer and one or more dielectric layers with one dielectric layer between the substrate surface and the metal layer. A connector is provided for applying a bias voltage to the metal layer with respect to the substrate. In effect, the metal layer of the band pass filter provides two functions. The first function is as part of the ITF filter selecting the wavelength desired for the device. The second function is as a conductive layer allowing a bias to be provided between the substrate and the metal layer thereby producing a field within the surface of the substrate to which the filter is applied.