Raytheon Company

Santa Barbara Research Center

David R Rhiger

Andrew Peter Clarke

Charles A Cockrum

William J Hamilton, Jr

Kelly A Jones

Sanghamitra Sen

Stuart B Farrell

Adam M Kennedy

Michael D Jack

Eric Frank Schulte

Justin Gordon Adams Wehner

George Grama

Kenneth Kosai

Jamal I Mustafa

Jeffrey M Peterson

Edward P Smith

Siddhartha Ghosh

Bernard Harris

Chad W Fulk

Leonard P Chen

Gerald A Garwood, Jr

James Pattison

Peter R Bratt

Ken J Ando

Stefan T A Baur

Owen K Wu

Chad M Althouse

An electrical device includes an aluminum nitride passivation layer for a mercury cadmium telluride (HgCdTe) (MCT) semiconductor layer of the device. The AlN passivation layer may be an un-textured amorphous-to-polycrystalline film that is deposited onto the surface of the MCT in its as-grown state, or overlying the MCT after the MCT surface has been pre-treated or partially passivated, in this way fully passivating the MCT. The AlN passivation layer may have a coefficient of thermal expansion (CTE) that closely matches the CTE of the MCT layer, thereby reducing strain at an interface to the MCT. The AlN passivation layer may be formed with a neutral inherent (residual) stress, provide mechanical rigidity, and chemical resistance to protect the MCT.

Aluminum nitride passivation layer for mercury cadmium telluride in an electrical device

In one aspect, a method includes forming an electrical path between p-type mercury cadmium telluride and a metal layer. The forming of the electrical path includes depositing a layer of polycrystalline p-type silicon directly on to the p-type mercury cadmium telluride and forming the metal layer on the layer of polycrystalline p-type silicon. In another aspect, an apparatus includes an electrical path. The electrical path includes a p-type mercury cadmium telluride layer, a polycrystalline p-type silicon layer in direct contact with the p-type mercury cadmium telluride layer, a metal silicide in direct contact with the polycrystalline p-type silicon layer, and an electrically conductive metal on the metal silicide. In operation, holes, indicative of electrical current on the electrical path, flow from the p-type mercury cadmium telluride layer to the electrically conductive metal.

Electrical contact fabrication

A sensing element of an infrared detector including a first absorber configured to form a first set of minority carriers upon receipt of an infrared flux, a collector, a first barrier disposed between the first absorber and the collector, a second absorber configured to form a second set of minority carriers upon receipt of the infrared flux, and a second barrier disposed between the second absorber and the collector. In response to a voltage being applied to the collector, the first and second set of minority carriers are collected at the collector.

Infrared detecting with multiple absorbers in a sensing element

A method for detecting both gamma-ray events and neutron events with a common detector, where the detector includes a layer of semiconductor material bounded by electrodes, and the electrodes include an anode on one side of the semiconductor material and a cathode on the other side of the semiconductor material, includes the following steps: (a) monitoring the electrical signal at each of the anode and the cathode; and (b) comparing the magnitude of the signals at the anode and the cathode, and the transit time difference between the start of the anode signal and the time when the anode signal reaches a maximum, relatively constant value. In the comparing step, predetermined criteria are used to differentiate between gamma-ray events and neutron events.

Combined neutron and gamma-ray detector and method

A method for detecting both gamma-ray events and neutron events with a common detector, where the detector includes a layer of semiconductor material adjacent one side of a glass plate and a Gd layer on an opposite side of the glass plate, between the glass plate and a layer of silicon PIN material to form an assembly that is bounded by electrodes, including a semiconductor anode on one side of the semiconductor layer, a cathode connected to the glass plate, and a Si PIN anode on a side of the Si PIN layer opposite the semiconductor anode. The method includes the steps of: (1) monitoring the electrical signal at each of the semiconductor anode and the Si PIN anode, and (2) comparing signals from the semiconductor anode and the SI PIN anode to differentiate between gamma-ray events and neutron events based on predetermined criteria.

Combined neutron and gamma-ray detector and coincidence test method

A method for detecting neutron radiation in accordance with particular embodiments includes exposing a neutron detector array comprising at least one two-dimensional array of neutron detectors to a first scene of interest. The neutron detector array is based on at least one two-dimensional array of microbolometer detectors. The method also includes receiving a plurality of response values from a corresponding plurality of neutron detectors of the neutron detector array. The method further includes generating a comparison value based on the plurality of response values and a baseline response value. The method additionally, includes determining whether more than a first threshold amount of neutron radiation is being generated by the first scene based on the comparison value.

Method and system for detecting neutron radiation

A neutron detector system including a neutron sensitive reaction layer may be configured to react with incident neutrons to form energetic particles. An energetic particle capturing layer may be configured to capture energetic particles emitted from the neutron sensitive reaction layer and convert the kinetic energy of the captured energetic particles to heat. A microbolometer sensing element responsive to the heat may be configured to detect the incident neutrons.

Neutron detection system

A method and apparatus for detecting gamma-rays is provided, wherein the gamma-ray detector apparatus includes a plurality of detector elements arranged in a stacked configuration. Each of the plurality of detector elements may include, a detector wafer having at least one anode separated from a cathode via a wafer material, wherein the wafer material includes a wafer material thickness d, and a wafer interface, wherein the wafer interface is electrically connected to the at least one anode.

Multi-layer pixellated gamma-ray detector

Impurities are extracted from a thin-film device structure based on mercury, cadmium, zinc, and/or tellurium, such as HgCdTe, CdTe, CdZnTe, or HgCdZnTe. The impurities are extracted by furnishing a sink medium comprising molten bismuth, and contacting the contaminated structure to the sink medium for a period of time sufficiently long that impurities diffuse out of the structure and into the bismuth for removal. The molten bismuth may additionally contain small amounts of one or more of the major components of the structure (mercury, cadmium, zinc, and/or tellurium) to inhibit loss of these elements from the structure.

Extraction of impurities from structures containing mercury, cadmium, zinc, or tellurium, and impurities

An array 1 of photodiodes 2 is comprised of a Group II-VI material, such as HgCdTe, which may be selectively doped to form a plurality of diode junctions. Array 1 is comprised of a plurality of photodiodes 2 which are disposed in a regular, two dimensional array. Incident IR radiation, which may be long wavelength, medium wavelength or short wavelength (LWIR, MWIR or SWIR) radiation, is incident upon a surface of the array 1. The array 1 comprises a radiation absorbing base layer 3 of Hg.sub.1-x Cd.sub.x Te semiconducting material, the value of x determining the responsivity of the array to either LWIR, MWIR or SWIR. Each of the photodiodes 2 is defined by a mesa structure, or cap layer 3; or the array 1 of photodiodes 2 may be a planar structure. Each of the photodiodes 2 is provided with an area of contact metallization 4 upon a top surface thereof, the metallization serving to electrically couple an underlying photodiode to a readout device. The upper surface of the array 1 is provided with, in accordance with the invention, a passivation layer 5 comprised of an epitaxial layer of Group II-VI material which forms a heterostructure with the underlying Group II-VI material and which has a wider bandgap than the underlying Hg(.sub.1-x)Cd.sub.x Te, thereby beneficially repelling both holes and electrons from the diode junctions.

Epitaxial passivation of group II-VI infrared photodetectors

A Group II-VI IR photodiode 10 has a passivation layer 16 overlying at least exposed surfaces of the p-n diode junction 15, the passivation layer being a compositionally graded layer comprised of Group II atoms diffused into a surface of the p-n diode junction. The passivation layer has a wider energy bandgap than the underlying diode material thereby repelling both holes and electrons away from the surface of the diode and resulting in improved diode operating characteristics. A cation substitution method of the invention includes the steps of preparing a surface to be passivated, such as by depleting an upper surface region of Group II atoms; depositing a layer comprised of a Group II material over the depleted surface region; and annealing the deposited layer and underlying Group II-VI material such that atoms of the deposited Group II layer diffuse into the underlying depleted surface region and fill cation vacancy sites within the depleted surface region. The resulting passivation layer is a compositionally graded layer having an energy bandgap which gradually decreases in value as a function of depth from the surface until the bandgap energy equals that of the underlying bulk material. The preparation of the surface may also be accomplished by providing a body of Group II-VI material which has a substantially stoichiometric composition.

Graded layer passivation of group II-VI infrared photodetectors

An imaging device (10, 10') has a plurality of unit cells (11) that contribute to forming an image of a scene. The imaging device includes a layer of wide bandgap semiconductor (18) material (e.g., silicon) having photogate charge-mode readout circuitry (20, 22, 24), such as CCD or CMOS circuitry, disposed upon a first surface of the layer. In one embodiment a second, opposing surface of the layer is bonded at a heterojunction interface or atomic bonding layer (16) to a surface of a layer of narrower bandgap semiconductor material (e.g., InGaAs or HgCdTe), that is selected for absorbing electromagnetic radiation having wavelengths longer than about one micrometer (i.e., the NIR or longer) and for generating charge carriers. The generated charge carriers are transported across the heterojunction interface for collection by the photogate charge-mode readout circuitry. The layer of narrower bandgap material may be disposed upon a surface of a transparent substrate, and also may be differentiated into a plurality of mesa structures (14a). In further embodiments the absorbing layer may have an equivalent or a wider bandgap than the layer having the readout circuitry.

Low light level imager with extended wavelength response employing

A three terminal solid-state ionizing radiation detector (10) includes a first layer (18) of a substantially intrinsic Group II-VI compound semiconductor material, such as CdZnTe. The first layer is responsive to incident ionizing radiation for generating electron-hole pairs. The detector further includes a second layer (24) of Group II-VI compound semiconductor material and a third layer (20) of Group II-VI compound semiconductor material that is interposed between first surfaces of the first layer and the second layer. The third layer functions as a grid layer. A first electrical contact (12, 17) is coupled to a second surface of the first layer, a second electrical contact (29, 30) is coupled to a second surface of the second layer, and a third electrical contact (22) is coupled to the third layer for connecting the detector to an external circuit that establishes an electric field across the detector. The electric field causes holes to drift away from the grid layer towards the first contact while electrons drift towards and through the grid layer, through the second layer, and towards the second contact for generating a detectable output signal pulse. Because of the presence of the grid layer only the electrons contribute to the output pulse. The grid layer has a conductivity type such that electrons are a minority charge carrier within the grid layer.

Single carrier-type solid-state radiation detector device

Gamma ray detectors (20, 130) are provided with a detector layer (30) that is formed of Hg.sub.x Cd.sub.1-x-y Zn.sub.y Te, wherein 0&lt;x&lt;0.05 and 0.ltoreq.y&lt;0.5. The Hg percentage in the group II sublattice of this detector layer is limited to replace Cd vacancies. These Cd vacancies are native point defects which degrade the resolution of gamma ray detectors because they facilitate early electron-hole recombination and time delays of current carriers.

Gamma ray detector with improved resolution and method of fabrication

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.

Growing community of inventors

Santa Barbara, CA, United States of America

David R Rhiger