Abstract: A dual-band HgCdTe radiation detector (10) includes a four layer n-p.sup.+ -p-n.sup.+ structure, grown by LPE, upon a substrate (12). The four layers are, from a bottom layer next to the substrate to the surface: (a) a MWIR radiation responsive n-type absorbing layer (14); (b) a p.sup.+ cap layer (16); (c) a LWIR radiation responsive p-type layer (18); and (d) an n+ top layer (20). The n.sup.+ top layer has a compositional profile that is similar to the p-type cap layer. Operation of this structure involves biasing the top layer positive with respect to the bottom layer, which results in the collection of LWIR-generated electrons in the p-type layer. Biasing the top layer negative with respect to the bottom layer results in MWIR-generated holes being collected by the bottom n-p+ junction.

Abstract: An uncooled thermal detector (10) includes a MIS capacitor (12) that is suspended from a material (26, 26a) having a low thermal conductivity. The MIS capacitor includes a doped semiconductor body portion (14) having a gate dielectric (20), a gate electrode (22), and a second electrode (24) disposed over a surface thereof. In operation, the capacitance of the MIS capacitor at a frequency near a high-frequency/low-frequency transition is measured or sensed. As the temperature of the MIS capacitor increases, the sensed capacitance increases because minority carriers are able to respond faster to a modulating gate voltage. Similarly, if the temperature decreases, the sensed capacitance decreases, because the minority carriers respond more slowly. A high thermal coefficient of capacitance (> 20%/K) is achieved at all gate bias values for which the MIS capacitor is in inversion.

Abstract: A layer (32) of a HgCdTe compound epitaxially contacts a buffer structure, which in turn epitaxially contacts a silicon substrate (22). The buffer structure is formed of II-VI compounds, and preferably includes at least one layer (24) of a ZnSeTe compound epitaxially contacting the silicon substrate (22) and a layer (30) of a CdZnTe compound overlying the ZnSeTe compound layer (24). The ZnSeTe compound layer (24) may be provided as a single graded layer having a composition of ZnSe adjacent to the silicon and a composition of ZnTe remote from the silicon, or as two distinct sublayers with a ZnSe sublayer (26) adjacent to the silicon substrate (22) and a ZnTe sublayer (28) remote from the silicon substrate (22).

Abstract: The light receiving or back-side surface (22) of an indium antimonide (InSb) photodetector device (10) substrate (12) is cleaned to remove all oxides of indium and antimony therefrom. Passivation and/or partially visible light blocking layers (26, 28) are then formed thereon of a material which does not react with InSb to form a structure which would have carrier traps therein and cause flashing. The optical cutoff wavelength and thickness of the partially visible light blocking layer (28) are selected to suppress the avalanche effect in the device (10) at visible wavelengths. This enables the device (10) to operate effectively over a wide wavelength range including the visible and infrared bands. The passivation and/or partially visible light blocking layers (26, 28) may be a thin layer of a semiconductor such as germanium, or silicon dioxide and/or silicon nitride followed by a partially visible light blocking silicon layer.

Abstract: The invention relates to a method for reducing a sidelobe impact of low order aberrations using a coronagraph (2) having an apodized occulting mask (10), comprising the steps of: (a) providing in the coronagraph (2) the apodized occulting disk (10) having a transmission profile which graduates from opaque to transparent along its radius and the negative of whose amplitude transmission is a Gaussian profile; (b) determining a predicted sidelobe impact of the aberrations from a particular mix of low order aberration measured in a system as described by the Zernike polynomials; (c) applying the coronagraph to a system point spread function using a given rms width for the Gaussian profile describing the apodized occulting mask (10) and determining an attenuation level of the aberration sidelobes; (d) scaling the Gaussian occulting mask (10) profile to a wider rms width if the sidelobe attenuation level is too low; and (e) repeating the steps (b) through (d) until the attenuation level is acceptable.

Abstract: A composite photodetector substrate is provided that can survive the expected functional stresses of a photodetector array and also reduce the number of photons that complete crosstalk paths in the radiation transparent substrates of typical prior photodetector arrays. The composite substrate includes a semiconductor substrate whose thickness is less than that required to survive typically expected functional stresses of the array, and a carrier bonded to the substrate to give the composite substrate the required strength. The reduced thickness of the semiconductor substrate increases the crosstalk path length which nonabsorbed photons travel between photodetectors. The increased path length includes a greater number of surface reflections, thus reducing the number of photons that complete the crosstalk path. The number is further increased by using a carrier that absorbs the radiation of interest.

Abstract: A dewar assembly is cleaned, baked out, assembled, and joined in a single vacuum system without exposing the components to ambient atmosphere. The vacuum system preferably has a first chamber with multiple subchambers that can be isolated from each other, and a second chamber that can be isolated from the first chamber. The multiple chambers and subchambers prevent cross contamination during the various process steps, and also permit multiple dewar assemblies to be batch processed at different stages simultaneously. The components of the dewar assembly are loaded into one subchamber and cleaned, and thereafter moved to another subchamber for bakeout. The dewar getter is heated in the second chamber and moved to one of the subchambers for assembly. The components of the dewar assembly are assembled and joined.

Abstract: An integrated radiation detector (10) includes a substrate (12) having a first region (14) comprised of Group III-V semiconductor material, such as GaAs, formed over a first surface, and a second region (26) comprised of Group II-VI semiconductor material, for example HgCdTe, formed over a second, opposite surface. The second region has a bandgap selected for absorbing radiation within a first range of wavelengths, such as IR radiation within the range of 12 micrometers to three micrometers. A first detector includes an antenna structure (20) coupled to a Schottky contact (22) for detecting electromagnetic radiation having wavelengths within a second range of wavelengths, such as wavelengths corresponding to frequencies within a range of approximately 30 GHz to approximately 1000 GHz. A second detector includes a photoconductive or photovoltaic infrared detector for collecting charge carriers generated by the absorption of the IR radiation.

Abstract: An infrared window (26) includes a substrate (40) made of a zinc salt composition and an antireflection coating system (42) deposited on the substrate (40). The coating system (42) comprises a first layer (44) of germanium overlying the substrate (40), a second layer (46) of diamond-like carbon overlying the first layer (44), a third layer (48) of germanium overlying the second layer (46), and a fourth layer (50) of diamond-like carbon overlying the third layer (48). Preferably, the germanium layers (44, 48) are in tension and the diamond-like carbon layers (46, 50) are in compression. The germanium layers (44, 48) are preferably deposited by magnetron sputtering and the diamond-like carbon layers (46, 50) are preferably deposited by plasma activated chemical vapor deposition. Silicon may be used in place of the germanium, and graded compositions can be used for the first layer (44) and the third layer (48).

Abstract: An integrated circuit, diode-based temperature sensor circuit (10) is amenable to fabrication upon a readout circuit (12) that is coupled during use to a FPA or radiation detectors. The sensor circuit is inherently self-calibrated, and provides for a cancellation of circuit offsets and other error sources. The circuit has an output that is time-multiplexed onto a data path that normally conveys a video data stream away from the readout circuit. The circuit operates to selectively forward bias a diode (D1) with two different currents. A difference between the currents is shown to indicate the temperature of the diode's p-n junction.

Abstract: A system (10) for detecting nitric oxide (NO) within an exhaust plume (14) includes a source (18) for generating an optical beam (20) and for directing (22, 24) the optical beam through the exhaust plume, the optical beam having wavelengths within a predetermined band of wavelengths within the infrared (IR) radiation spectrum. The system includes a sensor (32)/filter (30) assembly having a first channel for determining a measured NO transmission value for a first predetermined band of wavelengths; a second channel for determining a measured water transmission value for a second predetermined band of wavelengths; a third channel for determining a measured reference transmission value for a third predetermined band of wavelengths selected so as not to be significantly absorbed by the exhaust plume; and a fourth channel for determining a measured combustion by-product transmission value for a fourth predetermined band of wavelengths.

Abstract: A radiation detector includes a photovoltaic diode mesa structure (16) having of a plurality of sub-mesa structures (16a, 16b). Each of said sub-mesa structures includes a first layer (14a) of semiconductor material having a first type of electrical conductivity and a second layer (14b) having a second type of electrical conductivity such that a p-n junction is formed between the first and the second layers. Metalization (24) is disposed within a trench (30a) that runs between the sub-mesas and includes a tab portion (24a) that extends upwardly over a sidewall of each of said sub-mesa structures so as to electrically contact the second layer contained within each. As a result, each of said sub-mesa structures are electrically connected in parallel.

Abstract: An infrared dewar-detector assembly for use as a common module which is interchangeable between various military infrared detection systems. The detector is cooled to cryogenic temperature for improved sensitivity. The dewar of the common module incorporates a metal coldfinger mounted on a base plate for attachment to an associated cryo-engine. The coldfinger supports the detector on a beryllium bridge platform. The configurations of both the platform mount and the base plate are selected to minimize the vibrations transmitted to the detector.Signal paths from the detector include ribbon cables extending within the vacuum side of the dewar and having indium dot terminations making direct connections with a ceramic feedthrough header which, on the ambient pressure side of the unit, also includes indium pocket contacts for direct connection to the plug terminals of the unit.

Abstract: An ellipsometry cell is provided with a transparent lid that is positioned close to a specimen within the cell, thus allowing for a low volume wet chemical treatment of the specimen, and yet prevents interference with the ellipsometry measurements by partial reflections of a probe beam off the outer and inner lid surfaces. This is accomplished by configuring the lid to direct an ellipsometry beam and reflections thereof at different angles, so that the beam but not its reflections enter an ellipsometer analyzer. The lid preferably has an angled outer surface with beam entry and exit windows symmetrically tapering from a central ridge, and its inner surface substantially flat and parallel to the cell base.

Abstract: A photoresponsive device wherein the device includes semiconductor material, such as a cap region (14a), comprised of elements selected from Group IIB-VIA. A molybdenum contact pad (16) is formed upon a surface of the cap region, and a molybdenum ground contact pad is formed on a surface of a base region (12). A wide bandgap semiconductor passivation layer (20) overlies the surface of the cap region and also partially overlies the molybdenum contact pad. A dielectric layer (22) overlies the passivation layer, and an indium bump (24) is formed upon the molybdenum contact pad. The dielectric layer is in intimate contact with side surfaces of the indium bump such that no portion of the molybdenum contact pad can be physically contacted from a top surface of the dielectric layer. This method eliminates the possibility of unwanted chemical reactions occurring between the In and the underlying contact pad metal.

Abstract: A magnetoresistor (MR) and a non-magnetoresistor (NMR) are formed of indium antimonide or other magnetoresistive material in thermal proximity to each other on an integrated circuit substrate (100). Hall effect shorting strips (104) are formed on the magnetoresistor (MR) to make it much more magnetoresistive than the non-magnetoresistor (NMR). A current mirror (80) causes equal constant currents (I2) which do not vary with temperature to flow through the magnetoresistor (MR) and non-magnetoresistor (NMR), such that magnetoresistor and non-magnetoresistor voltages are developed thereacross respectively. The magnetoresistor and non-magnetoresistor voltages vary equally in accordance with temperature. The magnetoresistor voltage also varies in accordance with applied magnetic flux. A comparator (66) subtracts the non-magnetoresistor voltage from the magnetoresistor voltage to produce an output signal (Vout) with the temperature variation canceled, and which thereby varies only in accordance with magnetic flux.

Abstract: A P-type/intrinsic/N-type (P-I-N) gamma ray detector (10) includes a semiconductor detector layer (12) of intrinsic cadmium telluride (CdTe) or cadmium zinc telluride (CdZnTe). P- and N-doped semiconductor layers (14,16) of mercury cadmium telluride (HgCdTe) are formed on the opposite surfaces (12a,12b) of the detector layer (12), and ohmic metal contacts (18,20) are formed on the doped layers (14,16). The composition of the doped layers (14,16) is Hg.sub.1-x Cd.sub.x Te, and is graded such that x progressively decreases with distance from the detector layer (12) toward the ohmic contacts (18,20). This causes the bandgap of the doped layers (14,16) to also decrease from the detector layer (12) toward the ohmic contacts (18,20), forming potential barriers (E1,E2) which block leakage currents constituted by injection of minority carriers from the ohmic contacts (18,20) into the detector layer (12) and provide low resistance between the doped layers (14,16) and ohmic contacts (18,20).

Abstract: An array (10) of photoconductive (PC) radiation detectors includes a substrate (1) and a body (12) of PC material that is disposed upon the substrate. The body of PC material has a substantially linear shape. A plurality of electrical interconnects (14, 15) are electrically coupled to the body of PC material for differentiating the body into a plurality of radiation detector sites, individual ones of the plurality of radiation detector sites being disposed in a serial arrangement with one another along a length of the body of PC material. The array further includes a bias current input terminal (16) that is electrically coupled to a first end of the body of PC material and a bias current output terminal (18) that is electrically coupled to a second end of the body of PC material. As a result, a bias current that is applied to the bias current input terminal, and that is extracted from the bias current output terminal, flows through each of the plurality of serially disposed radiation detector sites.

Abstract: A vacuum package assembly (20) is prepared by self-welding the flanges (32 and 43) of two housings (28 and 36) together under an applied pressure, while the housings (28 and 36) and any enclosed structure or device are contained within an evacuated enclosure. The flanges (32 and 43) are preferably made of copper, with their respective self-welding members (34 and 46) specially prepared to enhance self-welding performance. The preferred treatment for the self-welding members (34 and 46) is to deposit a thin layer of nickel onto the self-welding members (34 and 46 ), deposit a thin layer of gold over the nickel, and heat the bonding member to elevated temperature to interdiffuse the gold into the self-welding member (34 and 46 ).

Abstract: A dual Joule-Thompson cryostat assembly (10) is provided which includes first and second concentrically aligned cryostats (100) and (102), respectively, which are disposed in the coldwell of a detector assembly (12). Each of the cryostats is connected to a source of pressurized gas which is discharged into the coldwell. The pressurized gas is directed at the components to be cooled such that the relatively high discharge velocity produces a relatively high film coefficient for maximizing heat transfer. Both the inner and outer cryostats, (100) and (102), respectively, of the dual cryostat assembly (10) are designed to direct pressurized gas at an electromagnetic detector (26). In addition, the inner cryostat (100) directs pressurized gas toward the outer cryostat (102) for precooling the outer cryostat (102). Furthermore, the outer cryostat (102) is designed to direct pressurized gas for cooling a coldshield (50) surrounding the detector (26).