Santa Barbara Research Center

Raytheon Company

William L Ahlgren

Eric Frank Schulte

William J Hamilton, Jr

Scott M Johnson

A semiconductor device comprises an active element and contacts that permit low-resistance external electrical connections. The active element includes an active layer formed from group II-VI elements, an n-doped layer on one side of the active it layer, and a p-doped layer on the other side of the active layer. The p-doped layer is a ZnSe-based alloy or a ZnTe-based alloy. There are electrical contacts to the n-doped layer and to the p-doped layer. The electrical contact to the p-doped layer includes a graded-alloy contact layer in epitaxial contact with the p-doped layer and whose bandgap varies from about that of the p-doped layer adjacent the p-doped layer to about zero at a location remote from the p-doped layer. The graded-alloy contact layer is a HgZnSSe-based graded-composition alloy where the p-doped layer is a ZnSe-based alloy, or a HgZnSeTe-based graded-composition alloy where the p-doped layer is a ZnTe-based alloy.

Ohmic contacts for p-type wide bandgap II-VI semiconductor materials

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).

Multilayer buffer structure including II-VI compounds on a silicon

A double layer heterojunction array 10 of IR photodiodes has formed within an upper planar surface region of a collector layer 16 a plurality of isolation junctions 20 which are disposed between individual photodiodes. The isolation junctions are formed by a thermally driven process of type-converting the p-type or n-type collector layer to the opposite type of material. This type conversion forms p-n homojunctions at the edges of the isolation junctions which isolate the individual photodiodes one from another. The type-conversion process of the invention provides two isotype junctions which together reflect excess minority charge carriers away from the surface of the device as well as from neighboring photodiodes. One method of the invention discloses the selective annealing of the surface of an n-type collector layer to extract mercury atoms thereby creating mercury vacancies which act as acceptors. Other methods disclose the type conversion as being accomplished by the selective diffusion of a dopant layer into the collector layer.

Planar double-layer heterojunction HgCdTe photodiodes and methods for

A photonic device includes a substrate and a region comprised of a quaternary Group II-VI material supported by the substrate. Examples of quaternary Group II-IV alloys include Hg, Zn, S and Se; Hg, Zn, Se and Te; Zn, S, Se and Te; Zn, Mn, S and Se; and Hg, Cd, Zn and S. By example, the quaternary material HgZnSSe, which is lattice-matched to ZnSe or GaAs, and the quaternary material HgZnSeTe, which is lattice-matched to ZnTe or GaSb, are employed in the construction of lasers, LEDs and detectors suitable for use over a range of wavelengths. The energy bandgap of the HgZnSSe alloy may be varied to achieve emission over the entire visible spectrum while the HgZnSeTe alloy emits within the spectrum from green to far infrared.

Quaternary II-VI materials for photonics

A reactor for laser-assisted CVD has a cylindrical symmetry and includes a high-speed horizontal rotating disk susceptor. The reactor of the invention provides for radiation, preferably UV laser radiation, to be introduced into the reactor radially along an axis. The radiation is constrained to occupy a thin region of space at or immediately adjacent to substrate surfaces upon which deposition is to occur. Preferably the radiation is provided as an annular beam that is reflected uniformly by a conical reflector to provide a relatively thin and uniform sheet of UV radiation that is approximately 0.1 mm to approximately 1.0 mm thick. In addition the reactor provides for Hg vapor, or any other gaseous reactant, to be introduced into the reactor at a same point on the axis as the laser radiation, separately from other reactants, and from a source coaxially disposed and external to the reactor.

Reactor for laser-assisted chemical vapor deposition

Apparatus and method for supplying elemental mercury to a MOCVD reactor during the operation of the reactor and for maintaining a saturated mercury vapor atmosphere over a surface of a substrate. A susceptor assembly 10 includes a susceptor 20 having a surface for supporting a substrate 22 within a growth chamber. A reservoir 34 of liquid mercury 36 is disposed external to the reactor and supplies liquid mercury via a capillary feed tube 30 to a depression or trough 24 formed within a surface of the susceptor at an upstream position from the substrate. Mercury within the trough is vaporized by the heated susceptor and flows over the substrate, thereby establishing a saturated mercury atmosphere over the substrate. The reservoir may be pressurized by a source of gas or its vertical position may be adjusted to provide a gravity feed of the mercury.

Elemental mercury source for metal-organic chemical vapor deposition

A method and apparatus for detecting infrared radiation is disclosed. The apparatus comprises a substrate (12) having readout and signal processing circuits (14) integrated therein. The substrate (12) is formed from a material selected from the group consisting of silicon, gallium arsenide, or germanium. A first semiconductor layer (28) is grown on the substrate (12) from a material selected from the group consisting of mercury-cadmium-telluride, mercury-zinc-telluride, mercury-cadmium-selenide, mercury-zinc-selenide, mercury-cadmium-sulfide, mercury-zinc-sulfide, lead-tin-telluride, lead-tin-selenide, lead-tin-sulfide, indium-arsenide-antimonide, gallium-indium-antimonide, or gallium-antimonide-arsenide. A second semiconductor layer (30) is then grown on the first semiconductor layer (28).

Method and apparatus for detecting infrared radiation

A method for forming an epitaxial layer upon a semiconductor substrate by vapor phase epitaxy is carried out within a quasi-open system having a controllably pressurized vertically orientated reaction chamber containing a charge of source material at a lower closed end. The chamber is heated at the lower end within a furnace such that the source material is vaporized. The substrate is introduced through an upper transfer chamber, passing through a gate valve so that it may be positioned by a moveable rod in a lower region of the chamber within the vapor given off by the source material. The source material vapor is deposited on the substrate, forming an epitaxial layer thereon. A cooling coil cools a portion of the chamber above the heated portion, thereby condensing the source vapor which may enter the cooled portion, such that the condensed vapor will remain in the lower, heated portion of the chamber. The transfer chamber and gate valve allow for maintaining the pressure within the chamber while the substrate is entered therein and during positioning. By varying the pressure within the chamber the composition of the vapor may be controlled and, hence, the composition of the epitaxial layer.

Vapor phase epitaxy of semiconductor material in a quasi-open system

Apparatus and method for supplying elemental mercury to a MOCVD reactor during the operation of the reactor and for maintaining a saturated mercury vapor atmosphere over a surface of a substrate. A susceptor assembly 10 includes a susceptor 20 having a surface for supporting a substrate 22 within a growth chamber. A reservoir 34 of liquid mercury 36 is disposed external to the reactor and supplies liquid mercury via a capillary feed tube 30 to a depression or trough 24 formed within a surface of the susceptor at an upstream position from the substrate. Mercury within the trough is vaporized by the heated susceptor and flows over the substrate, thereby establishing a saturated mercury atmoshere over the substrate. The reservoir may be pressurized by a source of gas or its vertical position may be adjusted to provide a gravity feed of the mercury.

Growing community of inventors

Goleta, CA, United States of America

William L Ahlgren