Monolithic extrinsic silicon infrared detector structure employing

Abstract

There is disclosed an all silicon monolithic focal plane array of infrared detectors for image detection. The structure comprises two epitaxial layers 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 first buried layer formed around a portion of the first epitaxial layer-substrate interface, and the charges are then transferred through a second buried layer of the same conductivity type to a conducting surface layer on the upper portion of the second epitaxial layer. The signal readout function is performed by a charge coupled device shift register constructed in the second epitaxial layer by providing selectively spaced electrodes in an insulating layer. Carriers generated in the detector by incident infrared radiation are collected into the first buried layer and then pass through the second buried layer to the surface layer and they 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 use of two epitaxial layers in the device improves its responsivity, its fill factor and better isolates the operation of its CCD circuits from its detector elements.