Abstract: A compositionally graded HgCdTe radiation detector (10) is constructed to have a high purity "denuded zone" (Region 2) that is formed adjacent to a radiation absorbing region (Region 1). The compositional grading results in an internally generated electric field that is orthogonally disposed with respect to an externally generated electric field applied between contacts (16, 18). The internally generated electric field has the effect of injecting photogenerated minority charge carriers into the denuded zone, thereby reducing recombination with photogenerated majority charge carriers and increasing carrier lifetime. The detector further includes a wider bandgap surface passivation region (Region 3) that functions to trap, or "getter", impurities from the denuded zone and also to reduce surface recombination effects.

Abstract: An array of photovoltaic radiation detectors and a method of fabricating same. The array 10 includes a substrate 12 substantially transparent to radiation having wavelengths of interest and a radiation absorbing base layer 14 having a first surface 14a overlying a surface of the substrate for admitting incident radiation into the base layer. The base layer is comprised of a compositionally graded p-type Hg.sub.1-x Cd.sub.x Te material wherein x equals approximately 0.6 to approximately 0.8 at the first surface and equals less than approximately 0.4 at a second surface 14b. A cap layer 16 overlies the second surface of the radiation absorbing base layer, the cap layer also being compositionally graded. The cap layer has a bandgap that increases in width as a function of distance from the second surface of the base layer.

Abstract: A mercury-cadmium-telluride photodiode array detector having a composite structure which includes a p-type HgCdTe substrate, a surface of which is implanted with n-type regions, thereby forming individual photodiodes of the array. Overlying this surface is a layer of insulating dielectric containing a buried layer of guard plate metalization. Overlying the dielectric is a layer of field plate metalization. Openings made through the field plate, dielectric, and guard plate allow for electrical contact with the individual photodiodes. The openings within the guard plate are made larger than those within the field plate. When these two plates are appropriately biased by external voltage sources, the substrate surface underlying the field plate and surrounding each diode is made to invert. The substrate surface underlying the guard plate remains at flat band potential, thereby electrically isolating the inverted surface surrounding each diode from the other inverted surfaces.

Abstract: A HgCdTe photodiode array for detecting mid-wavelength infrared radiation has a laminated structure consisting of a substrate, a heavily doped wide bandgap buffer layer, and a more lightly doped narrow bandgap base layer. Two sets of a orthogonally disposed U-shaped grooves are etched completely through the base layer and partially through the buffer layer, thereby forming a plurality of mesa-shaped structures. Overlying the portion of base layer contained within each mesa is a capping layer of opposite conductivity. The junction of the base and capping layer within each mesa forms a photodiode. In contact with each capping layer is a metalization area for connection of the underlying diode to a readout device. In contact with the buffer layer is another metalization layer for making a common electrical connection to the array of photodiodes. Overlying the mesa surfaces is a layer of passivation which contains a fixed positive charge.