Multiwavelength infrared focal plane array detector

Claim 1

A multiwavelength focal plane array light detector, comprising: a substrate doped to have a first conductivity, said substrate having top and bottom faces; a plurality of (N+1) absorption layers formed over the top of said substrate, where N=1,2,3,4. . . , the composition of each of said plurality of absorption layers being individually predetermined for absorbing or detecting different wavelengths of light, respectively; a plurality of (N-1) groups of light transparent buffer layers sandwiched between each successive pair of said plurality of (N+1) absorption layers, each of said groups of buffer layers including a plurality of buffer layers, said buffer layers of each group having successively decreasing bandgaps the further a buffer layer is from said substrate relative to other buffer layers of its associated said group of buffer layers, and at least all but one buffer layer of each said group of buffer layers having smaller bandgaps than the buffer layers of any other of said groups of said buffer layers closer to said substrate, respectively, relative to said substrate, for substantially preventing lattice mismatch dislocations from propagating through successive ones of said plurality of absorption layers, said buffer layers each having said first conductivity; a plurality of spaced apart holes formed from a top of said detector through selected successive ones of said absorption layers and buffer layers, for exposing predetermined areas of top portions of successive ones of said absorption layers, respectively, each of said exposed areas of said absorption layers being doped to form an underlying region in the associated absorption layer having a second conductivity opposite that of said first conductivity; a plurality of first ohmic contacts individually formed in a portion of the holes and on top of a portion of each of said exposed areas of said absorption layers; and a second ohmic contact formed on the bottom of said substrate, whereby a plurality of light detecting diodes are provided relative to each exposed area of said absorption layers, respectively, for individually detecting light of different wavelengths, respectively.