United States of America As Represented by the Secretary of the Air Force

Other

Solid State Scientific Corporation

G.t. Equuipment Technologies Inc.

David F Bliss

John S Bailey

Michael J Suscavage

Vladimir L Tassev

Michael J Callahan

Gerald W Iseler

Meckie T Harris

David W Weyburne

Robert M Hilton

Candace Lynch

William M Higgins

Mohan Chandra

Kedar Prasad Gupta

Ijaz H Jafri

Joseph A Adamski

Alton F Armington

Robert B Farmer

Bernard D Jones

Rick C White

Stephen Bachowski

Herbert E Bates

Buguo Wang

Brian G Demczyk

George G Bryant

George Bryant

David Gabbe

A new method for making a nonlinear optical structure for frequency conversion and for using that structure for frequency conversion is described. The nonlinear optical structure is made by depositing alternating contiguous layers of gallium arsenide and aluminum gallium arsenide onto a gallium arsenide substrate. Optical frequency conversion is performed by transmitting a pump laser beam through the structure. The new method is easier to perform than prior art methods.

Multi-layer gallium arsenide-based fresnel phase-shift device for infrared wavelength conversion

A method of hydrothermally synthesizing sapphire single crystals doped with trivalent metal ions in a crystal-growth autoclave including a crystal-growth zone and nutrient-dissolution zone in fluid communication with the crystal-growth zone is provided. Implementations of the method including situating within the crystal-growth zone at least one sapphire-based seed crystal and situating within the nutrient-dissolution zone an aluminum-containing material to serve as nutrient. An acidic, trivalent-metal-ion-containing growth solution is introduced into the cavity in a quantity sufficient, at least when heated to a predetermined average temperature, to immerse the at least one seed crystal and the nutrient in the growth solution. The growth solution is selected such that sapphire exhibits retrograde solubility therein and the growth process is carried out while maintaining an interior-cavity pressure within a range between and including each of 3.5 kilopounds per square inch and 25 kilopounds per square inch and while maintaining a temperature differential between the crystal-growth and nutrient-dissolution zones such that the average temperature within the crystal-growth zone is higher than the average temperature within the nutrient-dissolution zone.

Hydrothermal methods of fabricating trivalent-metal-ion-doped sapphire crystals

A new nonlinear optical structure for frequency conversion is described. The new nonlinear optical structure is a multilayer wafer comprising alternating layers of gallium arsenide and aluminum gallium arsenide onto a gallium arsenide substrate. The new device is both more efficient and easier to make than prior art gallium arsenide crystal structures designed for nonlinear optical conversion.

The invention provides for growing semiconductor and other crystals by loading a vessel in its lower portion with a seed crystal, loading a charge thereon in the vessel, heating the charge to a molten state and electromagnetically stirring the melt using magnetic and electric fields to obtain a more uniform composition of melt and slowly reducing the temperature of the melt over the crystal to grow a more uniform crystal from such stirred melt.

Growth of uniform crystals

Method and apparatus are provided for forming metal nitride (MN), wherein M is contacted with iodine vapor or hydrogen iodide (HI) vapor to form metal iodide (MI) and then contacting MI with ammonia to form the MN in a process of reduced or no toxicity. Such method is conducted in a reactor that is maintained at a pressure below one atmosphere for enhanced uniformity of gas flow and of MN product. The MN is then deposited on a substrate, on one or more seeds or it can self-nucleate on the walls of a growth chamber, to form high purity and uniform metal nitride material. The inventive MN material finds use in semiconductor materials, in nitride electronic devices, various color emitters, high power microwave sources and numerous other electronic applications.

Forming improved metal nitrides

Method and apparatus are provided for forming metal nitrides (MN) wherein M is contacted with iodine vapor or hydrogen iodide (HI) vapor to form metal iodide (MI) and contacting MI with ammonia to form the MN in a process of reduced or no toxicity. MN is then deposited on a substrate, on one or more seeds or it can self nucleate on the walls of a growth chamber, to form high purity metal nitride material. The inventive MN material finds use in semiconductor materials and in making nitride electronic devices as well as other uses.

Forming metal nitrides

This invention provides a process and apparatus for producing products of M-nitride materials wherein M&equals;gallium (GaN), aluminum (AlN), indium (InN), germanium (GeN), zinc (ZnN) and ternary nitrides and alloys such as zinc germanium nitride or indium aluminum gallium nitride. This process and apparatus produce either free-standing single crystals, or deposit layers on a substrate by epitaxial growth or polycrystalline deposition. Also high purity M-nitride powders may be synthesized. The process uses an ammonium halide such as ammonium chloride, ammonium bromide or ammonium iodide and a metal to combine to form the M-nitride which deposits in a cooler region downstream from and/or immediately adjacent to the reaction area. High purity M-nitride can be nucleated from the vapor to form single crystals or deposited on a suitable substrate as a high density material. High purity M-nitride single crystals can be grown by the direct reaction of the halide with the M-metal in a range of sizes from a few micrometers to centimeters, depending on the growth conditions. The small sized crystals are recovered as high purity M-nitride powder while the larger crystals can be prepared as substrates for electronic devices or UV/blue/green emitting diodes and lasers. The deposited layers can be used as M-nitride substrates, or targets for pulsed laser deposition (PLD), or other systems requiring high density targets. The deposition process, and subsequent density of the resulting component, is controlled by the reaction medium and by adjusting the temperature of the ammonium halide in an area near but separate from the reaction zone. Thickness of deposition on the substrates by the same process involves placement of the substrates in a suitable area in the reaction chamber and may be further controlled by the use of nitrogen, nitrogen-hydrogen mixtures or other suitable controlling gas to facilitate uniform distribution of the layer.

Process and apparatus for the growth of nitride materials

The present invention describes the growth of single crystals of non-congruently melting alloys, in particular, silicon-germanium of constant composition in a quartz ampoule by the use of CaCl.sub.2 as an encapsulant for the liquid encapsulated zone melting (LEZM) technique. The zone melting process was modified with the addition of calcium chloride which acts as a liquid encapsulant at temperatures above 660.degree. C. so that the crystal can grow without sticking to the container. The calcium chloride encapsulant creates a non-wetting buffer layer between the quartz container and the SiGe charge material allowing single crystal growth of mixed alloys. The crystal growth system consists of a vertical tube RF furnace with a water cooled split-ring concentrator. The concentrator is 5 mm. Thick by 25 mm diameter and provides a high temperature melt zone with a 'spike' profile. The single crystal seed and the polycrystalline alloy charge are loaded into a quartz ampoule which fits freely through the concentrator coil. The encapsulant calcium chloride is placed on top of the charge so that when it melts, it covers the inner surface of the quartz ampoule. During operation the alloy charge is melted in the 'spike' zone at the seed interface, and then the molten zone is translated along the length so that a single crystal of uniform composition is formed.

Silicon-germanium bulk alloy growth by liquid encapsulated zone melting

Using a GaN growth furnace, at least three different techniques can be used for forming the targets for the deposition of thin films. In the first, nitrides can be deposited as a dense coating on a target backing plate for use as a target. In this approach, the backing plate is placed near the Group III metal. During processing, the Group III metal or metal halide vaporizes and reacts with the nitrogen source to deposit a dense polycrystalline layer on the backing plate. To build up a thick layer on the backing plate, the backing plate is repeatedly placed in the processing furnace until a satisfactory thickness is attained. For the second approach, a properly shaped reaction vessel, the dense, thick Group III nitride crust that forms on top of the Group III metal during the process can be used directly or mechanically altered to meet the size requirements for a sputtering target holder. As a third approach, the Group III nitride material can be ground into a fine powder using traditional ceramic powder processing methods and then pressed to consolidate the powder into a sputtering target. The third processing option would typically lead to a low density target; however, this 'green' compact can then be reinserted into the same processing apparatus that the original powder was synthesized to infiltrate the open pores with the same or another group III metal nitride. This would produce a high density, thick target.

Process for the manufacture of group III nitride targets for use in

The invention is an improved method and apparatus for growing crystals that incorporates an isolation valve between the growth and injection chambers to allow the growth chamber to be maintained at operating temperature and pressure while decoupling the injector chamber in order to make changes necessary to restart or advance the process. Separate heating elements in the injector assembly or chamber provide related heating control. Upper and lower load cells and programmable signal amplifiers are configured to weigh and output the dynamic weight range of the loss or gain of process materials of the growth chamber crucible and the injector assembly, and are connected by electrical slip rings or wireless means to a computer control system.

Method and apparatus for synthesis and growth of semiconductor crystals

The present invention is an apparatus for the synthesis and growth of single crystals of phosphorus compounds starting with the elemental materials in a single furnace without external exposure. The apparatus of the present invention is a crystal growth furnace heated by RF coils. Inside the furnace is a susceptor heated by a lower coil device for holding a crucible. Above the crucible is selectively positioned a phosphorus improved injector. The improved injector is further surrounded by a susceptor which is heated by an upper coil device. The non-phosphorus materials are placed in the crucible and melted to a desired temperature. The phosphorus material previously placed within the injector is heated by the radiant heat from both crucible and the upper susceptor to drive the phosphorus vapor into the melt through a tube. This is closely controlled by noting the temperature within the injector and adjusting the height of the injector above the melt to control the temperature within the phosphorus material. After the formation of the stoichiometric melt, the seed is inserted into the melt for crystal growth if so desired. A further improvement to the above apparatus is the use of an improved injector having a cover and a shield thereabout. The injector and cover have a central hole through which the seed is inserted. The injector is moved vertically within the cover to provide the proper temperature therein.

Statement of government interest

New single crystals of ZnGeP.sub.2 are grown by a chemical vapor transport process from bulk synthesized polycrystalline ZnGeP.sub.2 using the LEK process with a controlled injection of phosphorus. The synthesis of the bulk is based on direct injection of phosphorus through a B.sub.2 O.sub.3 encapsulant and reaction with the zinc germanium melt, resulting in synthesis of a large melt (350 g) of ZnGeP.sub.2. When crystallization is followed by cooling the congruent melt down through the .alpha.-.beta. transition temperature (952.degree. C.) as is typical for bulk growth processes, the result is the growth of partially disordered material. This material is placed in a two zone heated furnace where iodine is used to transport the intermediate product to the growth zone where the single crystals grow, at a temperature below the .alpha.-.beta. phase transition. The resulting crystals produced contained a second cubic phase, which has not been reported previously.

Synthesis and growth processes for zinc germanium diphosphide single

The edge-defined, film-fed growth technique process is modified to produce a thin ribbon of bi-crystalline sapphire wherein the grain boundary is an essentially straight boundary and the angle is predetermined by selective cutting of the two seeds which are placed closely together during growth. The angle selection is optimized based on the superconducting material to be deposited and the application intended. After the ribbon is pulled, the ribbon is processed by cutting an appropriate section therefrom with the grain boundary. The substrate is polished and the high Tc superconducting material is deposited thereon to produce devices which rely on weak link Josephson junctions.

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Arlington, MA, United States of America

David F Bliss