University of California

Other

Max-planck-gesellschaft Zur F&#xf6;rderung Der Wissenschaften E. V.

Rockwell Int'l Corp.

Frederick F Lange

Jacob J Richardson

Steven P DenBaars

Daniel Bryce Thompson

Shuji Nakamura

Ingrid Koslow

David Bruce Marshall

Bhaskar V Velamakanni

Anthony G Evans

Jun Seok Ha

David Kisailus

Fritz Aldinger

Benjamin M Yu

Joseph J Ratto

Masa P Rao

Antonio Javier Sanchez Herencia

Jun-Seok Ha

Joachim Bill

Detlef Heimann

Robert Mehrabian

David C Lam

Jin Hyeok Kim

Craig A Folsom

Wen Chang Tu

A method for fabricating a Light Emitting Diode (LED) with increased light extraction efficiency, comprising providing a III-Nitride based LED structure comprising a light emitting active layer between a p-type layer and an n-type layer; growing a Zinc Oxide (ZnO) layer epitaxially on the p-type layer by submerging a surface of the p-type layer in a low temperature aqueous solution, wherein the ZnO layer is a transparent current spreading layer; and depositing a p-type contact on the ZnO layer. The increase in efficiency may be more than 93% with very little or no increase in cost.

Light emitting diodes with zinc oxide current spreading and light extraction layers deposited from low temperature aqueous solution

A method for synthesizing ZnO, comprising continuously circulating a growth solution that is saturated with ZnO between a warmer deposition zone, which contains a substrate or seed, and a cooler dissolution zone, which is contains ZnO source material.

Low temperature continuous circulation reactor for the aqueous synthesis of ZnO films, nanostructures, and bulk single crystals

A method of fabricating a Light Emitting Diode with improved light extraction efficiency, comprising depositing a plurality of Zinc Oxide (ZnO) nanorods on one or more surfaces of a III-Nitride based LED, by growing the ZnO nanorods from an aqueous solution, wherein the surfaces are different from c-plane surfaces of III-Nitride and transmit light generated by the LED.

Light emitting diode structure utilizing zinc oxide nanorod arrays on one or more surfaces, and a low cost method of producing such zinc oxide nanorod arrays

A high brightness III-Nitride based Light Emitting Diode (LED), comprising multiple surfaces covered by Zinc Oxide (ZnO) layers, wherein the ZnO layers are grown in a low temperature aqueous solution and each have a (0001) c-orientation and a top surface that is a (0001) plane.

High brightness light emitting diode covered by zinc oxide layers on multiple surfaces grown in low temperature aqueous solution

Reliable, flaw-tolerant brittle materials are produced by incorporating layers under residual compression on the surface and throughout the bulk of the material that act to trap and contain the propagation of otherwise catastrophic cracking. The residual compression within these layers acts to reduce the stress intensity of the cracks, thereby causing them to arrest until further loading is provided. This highly desirable stable, subcritical crack growth mode persists with increased loading until the applied stress is large enough to drive the crack completely through compressive region, after which failure occurs. The exact level of stress needed to accomplish this is dictated by the architectural design of the compressive layers such that the material can be designed to have any minimum strength desired, within the limits of the materials system used. This results in a truncation of the strength distribution, such that there is virtually zero probability of failure below this minimum value, i.e. the material possesses a threshold strength. Consequently, sensitivity to flaws that would ordinarily cause catastrophic failure at stresses below the threshold strength is eliminated. Furthermore, the potential exists for the complete elimination of the strength variability, hence improving reliability, through the creation of nearly deterministic, i.e. single-valued, strengths by increasing the threshold strength above the stresses at which failure normally initiates from intrinsic flaws.

Method for improving the reliability of brittle materials through the creation of a threshold strength

Colloidal isopressing provides a rapid method to form an engineering shape from a powder slurry, previously filtered to remove strength degrading inclusions. A slurry composed of a weakly attractive particle network, produced with a short-range, repulsive interparticle par potential, is consolidated to make a body with a high particle density that is easily fluidized by vibration. The fluid-like body is injected into a flexible mold and subjected to a larger isostatic pressure to force particles into contact. This creates a strong, elastic body with the shape of the mold. Because the particles are forced into contact at a high pressure, the liquid remaining within the component can be removed by evaporation without shrinkage, avoiding fracture during rapid drying.

Colloidal isopressing

A process for producing crystalline III-V compound films, preferably thin films of gallium nitride and other III-V nitrides, on various single crystal substrates. The process enables the preparation of III-V compound films by the simple, direct deposition of an amorphous layer of a III-V compound precursor on a single crystal substrate (as a template). A chemical reaction followed by a single heat treatment leads to the crystallization and formation of films by pyrolysis. According to specific examples of the invention, the chemical precursors gallium dimethyl amide (Ga &lsqb;N(CH ) &rsqb; ), gallium nitrate (Ga(NO ) , and gallium isopropoxide &lsqb;Ga(OC H ) are used to produce gallium nitride thin films.

III-V compound films using chemical deposition

Thin, single-crystal SiC films are obtained by means of a pyrolysis process, the substrate to be coated being covered with a carbonaceous polysilane, the adhering layer being pyrolyzed in an inert atmosphere and the amorphous layer of SiC obtained in this way being crystallized by maintaining it at a temperature of over 700.degree. C. Using a special variation of the process, it is easy to form doped SiC films. To this end the dopant is added in the form of a silane compound.

Formation of single-crystal thin SiC films

Damage-tolerant, continuous fiber ceramic matrix composites are fabricated to fill the space between the fibers with a powder. The powder particles are heat treated to form a porous framework without shrinkage, which is then strengthened with an inorganic synthesized from a precursor in solution. High particle packing densities is achieved within the fiber preform using a small particle-to-fiber diameter ratio. Filling the interstices with a powder increases the composite density and also limits the size of the crack-like voids within the matrix. The ceramic matrix composite (CMC) has mechanical characteristics similar to those found in wood. It is also affordable and inherently oxidation resistant. The composite is characterized by a heterogeneous distribution of fibers within a porous matrix having a homogeneous, fine porosity. A residual stress from thermal expansion mismatch of the matrix and fibers is created in the composite. The illustrated embodiment uses Al.sub.2 O.sub.3 fibers with either mullite or Si.sub.3 N.sub.4 matrices.

Damage tolerant ceramic matrix composites by a precursor infiltration

In a Ce-ZrO.sub.2 -based laminar composite having enhanced fracture toughness, alternating barrier layers comprise a ceramic material that undergoes stress-induced phase transformation, if any, less readily than Ce-ZrO.sub.2. Separation of the barrier layers is normally in the range of about 10-200 .mu.m, with optimum individual barrier layer thicknesses at the lower end of the range. Powders of ceramic materials comprising the individual layers of the composite are dispersed in separate slurries. The pH of the slurries is adjusted to form coagulations in which the particles settle without mass segregation and can be consolidated to high density by centrifuging. After centrifuging, the supernatant liquid can be removed and a desired volume of another slurry can be added on top of the first layer of consolidated material. This process can be repeated indefinitely to form a consolidated structure having individual layers as thin as approximately 10 .mu.m. The consolidated structure may be pressed, shaped, dried, and sintered to form the laminar composite. In the composite, interactions between a barrier layer and the martensitic transformation zone surrounding a crack or indentation spread the transformation zone along the region adjacent to the barrier layer. As a result, barrier layers provide large increases in toughness for cracks growing parallel or normal to the layers.

Partially stabilized ZrO.sub.2 -based laminar ceramic composites

A method of preparing dense ceramic product is described, wherein a coagulated network of ceramic powder particles in water is formed and then treated to increase the volume fraction of particles, thereby forming a water-saturated powder compact. The compact is formed into a desired shape and fired to provide the dense ceramic product. A coagulated network may advantageously be formed by mixing a ceramic powder with water at a pH that produces a net surface charge, to form a dispersed slurry and adding a sufficient amount of salt to the dispersed slurry to cause particles within the slurry to form the coagulated network. In view of the unique rheological properties of the powder compacts prepared from coagulated networks of ceramic powder particles, the compact may be processed into complex, near-net-shaped forms by introducing the compact into a mold and subjecting the mold to vibration, whereby the compact adopts the shape of the mold; once removed from the mold, the compact retains its shape without distortion.

Method for preparation of dense ceramic products

The present invention relates to processes to produce ceramic reinforced and ceramic-metal matrix composite articles. More specifically, the invention concerns the use of pressure filtration to infiltrate a reinforcing organic or inorganic network with ceramic particles. Centrifugation is also used to separate the liquid form the slurry. After heating the reinforced ceramic article is produced. Pressure filtration is also used to infiltrate an organic polymer or organic fiber network with ceramic particles. The solvent is removed carefully followed by intermediate heating to remove the organic network without deforming the preform shape. After densification, the preform is heated and contacted with molten metal (optionally) with pressure to infiltrate the open channel network. Upon cooling the ceramic metal matrix composite is obtained. The reinforced matrix articles are useful in high temperature and high stress applications, e.g., combustion chambers, space applications, ceramics for bathroom fixture use, and the like. A significant advantage of this process is its ability to manipulate the architecture as well as the amount of metal reinforcement in the composite as per specifications. Moreover, one can choose different metal-ceramic reinforcements as per the processing needs.

Method to produce ceramic reinforced or ceramic-metal matrix composite

The present invention relates to an article having improved physical properties as compared to the individual components, which article comprises:

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Santa Barbara, CA, United States of America

Frederick F Lange