Control of optical crosstalk between adjacent photodetecting regions

An array of radiation responsive photodiodes comprising:

• a substrate;
• a layer of radiation absorbing semiconductor material having a first electrical conductivity disposed upon a surface of said substrate, said layer generating minority charge carriers from absorbed radiation, said layer being comprised of compositionally graded material such that said layer has a first energy bandgap at a first surface adjacent to the surface of said substrate and a second, narrower energy bandgap at a second surface opposite the first surface, the narrower energy bandgap of the second surface constraining a lateral diffusion of the charge carriers to occur within a region substantially adjacent to said second surface, said layer further including a plurality of regions having an opposite type of conductivity for forming a plurality of p-n junctions for collecting said minority charge carriers;
• and
• a plurality of groove structures formed within the second surface of said layer and extending into said layer to a depth which is less than a thickness of said layer, individual ones of said groove structures being interposed between at least two adjacent ones of said p-n junctions for substantially preventing a charge carrier from laterally diffusing from within an area surrounding one of said p-n junctions to an area surrounding another one of said p-n junctions.