Monolithic extrinsic silicon infrared detectors with an improved charge

Abstract

There is disclosed an all silicon monolithic focal plane array of infrared detectors for image detection. The structure comprises an epitaxial layer grown on an extrinsically doped silicon substrate. The detectors are formed in and extend through the substrate, the material of which is sensitive to specific wavelength infrared signals according to the dopant used in the substrate. The collection of charges takes place on a buried layer formed around a portion of the epitaxial layer-substrate interface, and the charges are then transferred through a surface layer of the same conductivity type to the surface of the epitaxial layer. The signal readout function is performed by a charge coupled device shift register constructed in the epitaxial layer by providing selectively spaced electrodes in an insulating layer. Carriers generated in the detector by incident infrared radiation are collected into the buried layer and then pass through the surface layer, are injected therefrom into the CCD shift register and are detected at the output. The monolithic construction and the use of an epitaxial layer to form the CCD shift register result in high yield and high efficiency devices. The planar surface of the device improves the aluminum step coverage for a more reliable device, and the use of the buried layer improves the fill factor of the detector.