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

Meckie T Harris

Alton F Armington

David F Bliss

John J Larkin

Michael J Suscavage

John S Bailey

Michael J Callahan

William M Higgins

John K Kennedy

J Emery Cormier

George G Bryant

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

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

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 growth of bismuth silicate crystals occurs in a high pressure vessel or autoclave using a hydrothermal growth process. The nutrient material is placed in a sealed container of noble metal, liner, along with a solvent to a selected fill level. A filler fluid is also placed between the liner and the pressure vessel. The oriented seeds are placed in the cooler top seed zone over a baffle that slows the movement of supersaturated liquid from the hotter lower nutrient zone. Using a selected heating schedule for the top and the bottom zones, a plurality of large crystals are grown in the seed zone. The temperature differential is about 5.degree. C.

Hydrothermal growth on non-linear optical crystals

A composite susceptor for a radio frequency (RF) heated crystal growing furnace has a plurality of stacked electrically insulating and electrically conducting elements about the crucible area so that a proper temperature gradient is established and controlled.

Apparatus and method for controlling gradients in radio frequency heating

Ultra high pure quartz is grown by a one step in-situ growth process where the nutrient is high purity silica. A negative temperature gradient is maintained between the nutrient zone and the seed zone until about the start of crystal growth. A sealable container made of silver contains the nutrient and the seed within the autoclave chamber.

Growing community of inventors

Nashua, NH, United States of America

Meckie T Harris