Light emitter with metal-oxide coating

• US 20130228808A1
• Filed: 12/06/2005
• Published: 09/05/2013
• Est. Priority Date: 12/06/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: eLite Optoelectronics, Inc. (Bridgelux Incorporated)
• Inventors: Lester, Steven D.
• Granted Patent: US 8,729,580 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A light emitting device based on a AlInGaN materials system wherein a coating is used to improve the extraction of light from a device. A coating has a very low optical loss and an index of refraction greater than 2. In a preferred embodiment the coating is made from Ta₂O₅, Nb₂O₅, TiO₂, or SiC and has a thickness between about 0.01 and 10 microns. A surface of a coating material may be textured or shaped to increase its surface area and improve light extraction. A surface of the coating material can also be shaped to engineer the directionality of light escaping the layer. A coating can be applied directly to a surface or multiple surfaces of a light emitting device or can be applied onto a contact material. A coating may also serve as a passivation or protection layer for a device.

Claims

1. A light emitting device comprising:

a substrate portion;

a light emitting portion in contact with the substrate portion; and

a coating layer portion comprising a first and second coating layer wherein the first coating layer is in direct physical contact with the light emitting portion and has an index of refraction greater than 2 and an optical loss factor less than 0.2 and the second coating layer is in direct physical contact with the first coating layer and has a top surface with a three dimensional pattern chosen from a group consisting of ribs, cylinders, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, ellipsoids, hemispheres, rectilinear trenches, rectilinear solids, cones, angled cylinders, angled hemispheres, angled ellipsoids, angled rectilinear trenches, angled solids and angled cones and wherein element to element spacing may be uniform or not wherein said coating layer portion is chosen from a group consisting of metal oxides, silicon carbide, Ta₂O₅, Nb₂O₅, TiO₂, and their non-stoichiometric mixtures.

2. The light emitting device of claim 1 wherein said light emitting portion comprises:

a first cap layer of a first conductivity type adjacent to said substrate portion;

an active region comprising one or more layers separated from said substrate portion by the first cap layer;

a second cap layer of a second conductivity type;

one or more contact layers in contact with the active region through the second cap layer; and

one or more electrode layers in contact with one of the one or more contact layers.

4. The light emitting device of claim 1 wherein said substrate portion is chosen from a group comprising sapphire, silicon carbide, GaN, and silicon.

3. (canceled)

5-19. -19. (canceled)