Photodiode array

Claim 1

In an image detector system having an array of diode detectors, sensitive to light in a given frequency band, mounted on a thick high resistance substrate transparent to light in said band; the improvement wherein: said array comprises three thin superposed coextensive layers of epitaxially grown semiconductive material doped to provide a different conductivity in each of said layers; the second or center layer of said three layers being formulated to provide energy-band gaps which highly absorb energy in said selected band thereby generating therein a high density of photocurrent in response to said radiation; a first or top layer of said three layers doped to provide current carriers having a conductivity opposite to said second layer, thereby forming a photodiode; a third or bottom layer of said three layers doped to have the same conductivity type but greater conductivity than said second layer thereby providing good ohmic contact between all points on the adjacent surface of said second layer; said first and third layers being formulated to be transparent to energy in said selected band, and each having a broad surface spaced from said second layer; an array of equally spaced ohmic metal contacts arranged in rows and columns attached to said broad surface of said first layer; and said three layers defining at least two series of grooves with a groove between every adjacent parallel pair of said rows and columns of said contacts, the grooves in different series intersecting, and said grooves penetrating the full depth of said first and second layers plus a very small fraction of said third layer, whereby said contacts are mounted on isolated portions of said first and second layers connected only through said third layer.