USA As Represented by Secretary of the Navy

The Aerospace Corporation

Richard B Schoolar

James D Jensen

Alfred A Fote

A semiconductor photoconductor having low impedance nonmetallic contacts is disclosed which has increased detectivity over prior art photoconductor structures. The improved photoconductor has metallic contacts that are separated by a contact length that is greater than the optical length of the detector. The contact regions of the semiconductor adjacent the detector region are thicker than the detector region. The process for fabricating the photoconductor includes thinning the detector region to an appropriate thickness while preserving the greater thickness of the contact regions.

Thick extended contact photoconductor

A variable temperature method for the preparation of single and multiple taxial layers of single-phase (e.g., face-centered cubic), ternary lead chalcogenide alloys (e.g., lead cadmium sulfide [Pb.sub.1-w Cd.sub.w ].sub.a [S].sub.1-a wherein w varies between zero and fifteen hundredths, inclusive, and a=0.500.+-.0.003), deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the temperature of the substrate is varied, thereby providing an epilayer with graded composition and predetermined electrical and optical properties along the direction of growth. This growth technique can be used to produce infrared lenses, narrowband detectors, and double heterojunction lasers.

Graded gap semiconductor optical device

A high temperature method for the preparation of single and multiple epitaxial layers of single-phase lead sulfide-selenide, [Pb].sub.a [S.sub.x Se.sub.1-x ].sub.1-a wherein x varies between one and zero, inclusive, and a=0.500.+-.0.003, deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the substrate is exposed to the vapor emanating from the single chimney of a two-zone, dual-chamber furnace, thereby providing an epilayer of uniform, and predetermined electrical and optical properties.

PbS.sub.x Se.sub.1-x semiconductor

A thin-film single-crystal infrared detector exhibiting an increased frequency of response. A closed transverse junction, formed by diffusing a central electrode of an impurity rich metal into a lead-salt film epitaxially grown on an insulating substrate, provides an effective optical area in excess of the junction surface. An ohmic contact is spaced apart from the central electrode. Junction capacitance, a limitation upon the electrical response, is diminished by the detector geometry while detectivity is enhanced. In an alternative embodiment the detector may be segmented to provide directional detection.

Method of preparing a thin-film, single-crystal photovoltaic detector

A variable temperature method for the preparation of single and multiple epitaxial layers of single-phase (e.g., face-centered cubic), ternary lead chalcogenide alloys (e.g., lead cadmium sulfide, [Pb.sub.1-w Cd.sub.w ].sub.a [S].sub.1-a wherein w varies between zero and fifteen hundredths, inclusive, and a=0.500.+-.0.003), deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the temperature of the substrate is varied, thereby providing an epilayer with graded composition and predetermined electrical and optical properties along the direction of growth. This growth technique can be used to produce infrared lenses, narrowband detectors, and double heterojunction lasers.

Pb.sub.1-W Cd.sub.W S Epitaxial thin film

A variable temperature method for the preparation of single and multiple taxial layers of single-phase (e.g., face-centered cubic), ternary lead chalcogenide alloys (e.g., lead cadmium sulfide, [Pb.sub.1-w Cd.sub.w ].sub.a [S].sub.1-a where w varies between zero and fifteen hundredths, inclusive, and a=0.500.+-.0.003), deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the temperature of the substrate is varied, thereby providing an epilayer with graded composition and predetermined electrical and optical properties along the direction of growth. This growth technique can be used to produce infrared lenses, narrowband detectors, and double heterojunction lasers.

Graded gap semiconductor detector

A thin-film single-crystal infrared detector exhibiting an increased freqcy of response. A closed transverse junction, formed by diffusing a central electrode of an impurity rich metal into a lead-salt film epitaxially grown on an insulating substrate, provides an effective optical area in excess of the junction surface. An ohmic contact is spaced apart from the central electrode. Junction capacitance, a limitation upon the electrical response, is diminished by the detector geometry while detectivity is enhanced. In an alternative embodiment the detector may be segmented to provide directional detection.

High electrical frequency infrared detector

A variable temperature method for the preparation of single and multiple taxial layers of single-phase (e.g., face-centered cubic), ternary lead chalcogenide alloys (e.g., lead cadmium sulfide, [Pb.sub.1-w Cd.sub.w ].sub.a [S].sub.1-a wherein w varies between zero and fifteen hundredths, inclusive, and a=0.500.+-.0.003), deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the temperature of the substrate is varied, thereby providing an epilayer with graded composition and predetermined electrical and optical properties along the direction of growth. This growth technique can be used to produce infrared lenses, narrowband detectors, and double heterojunction lasers.

Growth technique for preparing graded gap semiconductors and devices

Method of fabricating a high electrical frequency infrared detector by

Equilibrium growth technique for preparing PbS.sub.x Se.sub.1-x epilayers

The process of coating epitaxial films of lead chalcogenide materials with s.sub.2 S.sub.3 to insulate the films from the effects of oxygen upon exposure to air.

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Silver Spring, MD, United States of America

Richard B Schoolar