Light Emitter with Coating Layers

• US 20140124806A1
• Filed: 10/27/2009
• Published: 05/08/2014
• Est. Priority Date: 12/06/2005
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Bridgelux Incorporated
• Inventors: Lester, Steven D.
• Application Number:
  US12/607,053
• Publication Number:
  US 20140124806A1
• 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

An AlInGaN light emitting device having 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, preferably having an index of refraction close to or greater than the index of refraction of GaN. The coating can be made from Ta₂O₅, Nb₂O₅, TiO₂, or SiC and has can have a thickness between 0.01 and 10 microns. A surface of the coating material may be textured or shaped to increase its surface area and improve light extraction. A coating can be applied directly to one or multiple surfaces of the light emitting device or can be applied onto a contact material and can serve as a passivation or as a protection layer for a device.

Claims

1. A light emitting device comprising:

a first substrate portion;

a light emitting portion in contact with a first coating layer portion, the first coating layer portion in contact with the first substrate portion, wherein a reflective layer structure is integral to the first coating layer portion; and

a second coating layer portion in contact with the light emitting portion wherein at least one of the first and second coating layer portions has a continuous pattern having a cross section chosen from a group consisting of ribs, cylinders, slots, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, cylinders, 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 and wherein at least one of the first and second coating layer portions has an index of refraction greater than about 2 and an optical loss factor less than about 0.2.

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

a first cap layer of a first conductivity type disposed on a side of the light emitting portion, the side of the light emitting portion facing the first substrate portion;

an active region comprising one or more layers separated from said first 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

wherein said active region is of an AlInGaN material system.

4. The light emitting device of claim 1 wherein said first and

second coating layer portions are chosen from a group comprising metal oxides, silicon carbide,

GaN, Ta20s, Nb20s, Ti02, AlInGaN based solid solutions, and their non-stoichiometric mixtures.

5. The light emitting device of claim 1 wherein said second coating layer portion comprises one or more coating layers wherein at least a first of the one or more coating layers of said second coating layer portion has an index of refraction greater than 2 and an optical loss factor less than 0.2.

2. (canceled)

6. (canceled)

7. A light emitting device comprising:

a first substrate portion;

a reflective layer directly and physically in contact with the first substrate portion;

a transparent conductive layer in contact with the reflective layer;

a light emitting portion comprising at least two layers, wherein the light emitting portion is directly and physically in contact with the transparent conductive layer; and

one or more coating layers adjacent the light emitting portion having a pattern having a cross section chosen from a group consisting of ribs, cylinders, slots, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, cylinders, 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 at least a first coating layer of the one or more coating layers has an index of refraction greater than 2 and an optical loss factor less than 0.2.

9. The light emitting device of claim 7 wherein said light emitting portion further comprises:

a first cap layer of a first conductivity type disposed on a side of the light emitting portion, the side of the light emitting portion facing the first substrate portion;

an active region comprising one or more layers separated from said first 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;

wherein said active region is of an AlInGaN material system.

10. The light emitting device of claim 7 wherein said one or more coating layers are chosen from a group comprising metal oxides, silicon carbide, GaN, Ta20s, Nb20s, Ti02, AlInGaN based solid solutions, and their non-stoichiometric mixtures.

8. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. A light emitting device comprising:

a first substrate portion;

a light emitting portion in contact with a first coating layer portion, the first coating layer portion in contact with the first substrate portion wherein a reflective layer structure is integral to the first coating layer portion; and

a second coating layer portion in contact with the light emitting portion wherein at least one of the first and second coating layer portions has a continuous pattern having a cross section chosen from a group consisting of ribs, cylinders, slots, polygon shaped ribs, triangular shaped ridges, hemispherical shaped mounds, horizontal cylindrical shaped ribs, cylinders, 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 and wherein at least one of the first and second coating layer portions has an index of refraction greater than about 2 and an optical loss factor less than about 0.2.