Signal detection method for ir detector having charge readout structure

Abstract

A method and apparatus for improving the operation of infrared detectors of a type generally characterized by a semiconductive substrate of a first conductivity type which includes a detection region defined or bounded by a heavily doped backside electrode and buried layer of the first conductivity type. A charge coupled device (CCD) readout structure for transfers charge in an epitaxial layer of second conductivity type which overlies the substrate, and the detector further includes a heavily doped layer of the second conductivity type positioned between the epitaxial layer and the substrate to shield the charge carriers of the substrate from the CCD voltages. Means are provided by the present invention for the injection of minority charge carriers into the epitaxial region which are subsequently transferred to output means by the CCD. The substrate is biased so that a portion of the flow of minority carriers in the epitaxial layer will be diverted toward the backside electrode when the detection region is raised to conduction by the incidence of photon energy so that a subtractive indication of the radiation is obtained while harmful double injection and attendant substrate breakdown are avoided.