Texas Instruments Corporation

Raytheon Company

Herbert F Schaake

John H Tregilgas

Jeffrey Don Beck

Michael A Kinch

Luigi Colombo

Malcolm John Bevan

Donald F Weirauch

Sebastian R Borrello

Carlos A Castro

Roland J Koestner

Kent R Carson

This is a sensor for, and a method of, determining if a particular type of flame is present, using at least two uncooled HgCdTe detector films on a common IR transmissive substrate. Specific examples of the types of radiation which can be identified include gasoline flames, natural gas flames, and organic combustion flames (identified, e.g., by comparing the amount of combined carbon dioxide and carbon monoxide to the amount of water vapor). The ratio of carbon dioxide to carbon monoxide can also be determined. The sensor can include a first HgCdTe filter (88) on a common IR transmissive substrate (42), a first uncooled HgCdTe detector film (86) over the first filter (88), and a second uncooled HgCdTe detector film (92) on a CdTe insulator which is either on the first uncooled HgCdTe detector film, or on a second HgCdTe filter (94) provided on the common IR transmissive substrate.

Uncooled infrared sensors for the detection and identification of

Films of Hg.sub.1-x Cd.sub.x Te grown at low temperatures by MBE or MOCVD are homogenized by annealing at about 350.degree. C. for 1.25 to 3 hours.

Homogenization anneal of II-VI compounds

The disclosure relates to a method for reducing impurity concentration in mercury cadmium telluride alloys wherein impurities are attracted to a region saturated with second phase tellurium during annealing in a saturated mercury atmosphere where the second phase tellurium and the impurities attracted thereto can be removed by polishing, etching, grinding, or the like.

Impurity reduction technique for mercury cadmium telluride

The disclosure relates to a method for removing the unwanted impurities from an HgCdTe alloy which consists of the steps of depositing a thin film on the order of from about 1 to about 100 microns in thickness of tellurium onto the backside of a mercury cadmium telluride bar to insure the presence of a substantial amount of excess tellurium on the backside of the alloy bar and allow the gettering mechanism to work. A protective film to shield the tellurium film from mercury ambient atmosphere is then optionally placed over the tellurium film. The protective film can be formed of a silicon oxide such as SiO and is preferably in the range of about 1000 angstroms to 10 microns or more in thickness. The bar with the tellurium and protective film thereon is then annealed at a temperature of less than 450.degree. C., preferably about 280.degree. C., for a period of from about one day to about four weeks in a saturated mercury atmosphere to allow the impurities in the alloy to diffuse to the backside thereof and into the tellurium layer. The bulk of the impurities will travel into the tellurium layer within a matter of several days at the preferred temperature noted hereinabove. The tellurium layer and protective film are then removed such as by grinding, etching or other appropriate method to remove the impurities from the alloy bar.

Gettering method for mercury cadmium telluride

The disclosure relates to a method for making extrinsically doped HgCdTe alloys containing Cu, Ag, or Au or other dopant impurity whereby the excess tellurium in the core is annihilated (stoichiometrically compensated by excess in-diffusing Hg) and the dopant impurities are then permitted to randomly move through the slab to provide for homogeneity thereof. A post-annealing step of much greater than normal temperature-time length than was provided in the prior art is used. A standard post-annealing step in a saturated mercury vapor atomosphere leaves second phase tellurium (and gettered impurities) at the center of the slab, and longer term post-annealing negates this situation by annihilating the second phase tellurium in the slab and thus permitting the impurities to randomly travel by solid state diffusion throughout the slab to ultimately be distributed therein in a homogeneous manner. The additional time required for the post-annealing step following the normal prior art post-annealing step varies based upon slice or slab thickness, the metal-Te stoichiometry, and second post-annealing step temperature and, in general, will be longer but in the same range as that used in the prior post-annealing stage. Following annihilation of the second phase tellurium from the core, the impurity is homogenized in the slab by further annealing for from about one hour to about 20 weeks at a temperature under 300.degree. C., preferably 280.degree. C., by solid state diffusion.

Method of producing homogeneously doped HgCdTe which contains a fast

The dislocation density near the surface of Hg.sub.1-x Cd.sub.x Te alloys is substantially reduced by annealing the material at around 600.degree. C. in a mercury saturated ambient for periods of four hours or more, prior to post annealing at lower temperatures to control the metal vacancy concentration. This procedure allows dislocation reduction by climb, reduces the concentration of metal vacancies which can collapse to form dislocation loops or contribute to dislocation multiplication, and reduces tellurium precipitates which contribute to dislocation multiplication during subsequent post annealing.

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Denton, TX, United States of America

Herbert F Schaake