Enhanced brightness light emitting device spot emitter

• US 6,730,940 B1
• Filed: 10/29/2002
• Issued: 05/04/2004
• Est. Priority Date: 10/29/2002
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Keuper, Matthijs H., Steranka, Frank M., Steigerwald, Daniel A.
• Primary Examiner(s): PRENTY, MARK V
• Application Number:
  US10/283,737
• Publication Number:
  US 20040079942A1
• Time in Patent Office: 553 Days
• Field of Search: 257/98, 257/99, 257/741
• US Class Current: 257/98
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

The amount of usefully captured light in an optical system may be increased by concentrating light in a region where it can be collected by the optical system. A light emitting device may include a substrate and a plurality of semiconductor layers. In some embodiments, a reflective material overlies a portion of the substrate and has an opening through which light exits the device. In some embodiments, reflective material overlies a portion of a surface of the semiconductor layers and has an opening through which light exits the device. In some embodiments, a light emitting device includes a transparent member with a first surface and an exit surface. At least one light emitting diode is disposed on the first surface. The transparent member is shaped such that light emitted from the light emitting diode is directed toward the exit surface.

Claims

1. A light emitting device comprising:

a substrate having a first surface and a second surface opposite the first surface;

a region of first conductivity type overlying the first surface of the substrate;

an active region overlying the region of first conductivity type;

a region of second conductivity type overlying the active region; and

a reflective material overlying a portion of the second surface of the substrate, the reflective material surrounding an aperture through which light exits the device;

wherein the substrate is transparent to light emitted by the active region.

5. The light emitting device of claim 1 wherein the reflective material is a metal.

6. The light emitting device of claim 5 wherein the metal has a reflectance greater than 90%.

7. The light emitting device of claim 5 wherein the metal is selected from the group consisting of silver, gold, aluminum, and rhodium.

8. The light emitting device of claim 1 wherein the reflective material is a non-specular (white) layer.

9. The light emitting device of claim 8 wherein the non-specular layer comprises barium sulfate.

10. The light emitting device of claim 8 wherein the non-specular layer is insulating.

11. The light emitting device of claim 1 further comprising an optical system positioned near the second surface of the substrate.

12. The light emitting device of claim 11 wherein the portion of the substrate covered by the reflective material is outside an area corresponding to an etendue-limit of the optical system.

19. The light emitting device of claim 1 wherein the aperture is located substantially in a center of the device.

20. The light emitting device of claim 1 wherein the aperture is one of circular and rectangular.

21. The light emitting device of claim 1 wherein light exiting from the aperture comprises the primary light output of the device.

2. A light emitting device comprising:

a substrate having a first surface, a second surface opposite the first surface, and a first side substantially perpendicular to the second surface;

a region of first conductivity type overlying the first surface of the substrate;

an active region overlying the region of first conductivity type;

a region of second conductivity type overlying the active region;

a reflective material overlying a portion of the second surface of the substrate, the reflective material surrounding an aperture through which light exits the device; and

a reflective material covering a portion of the first side.

3. The light emitting device of claim 2 wherein the reflective material covering the portion of the substrate is the same as the reflective material covering a portion of the first side.

4. The light emitting device of claim 2 wherein the reflective material covering the portion of the substrate is a different material from the reflective material covering a portion of the first side.

13. A light emitting device comprising:

a substrate having a first surface and a second surface opposite the first surface;

a region of first conductivity type overlying the first surface of the substrate;

an active region overlying the region of first conductivity type;

a region of second conductivity type overlying the active region;

a reflective material overlying a portion of the second surface of the substrate, the reflective material surrounding an aperture through which light exits the device;

wherein the reflective material is separated from the substrate by a transparent material.

14. The light emitting device of claim 13 wherein the transparent material comprises a dome.

15. The light emitting device of claim 13 wherein the transparent material comprises a fresnel lens.

16. The light emitting device of claim 13 wherein:

the substrate has a first index of refraction;

the transparent material has a second index of refraction; and

the second index of refraction is greater than or equal to the first index of refraction.

17. A light emitting device comprising:

a substrate having a first surface and a second surface opposite the first surface;

a region of first conductivity type overlying the first surface of the substrate;

an active region overlying the region of first conductivity type;

a region of second conductivity type overlying the active region;

a reflective material overlying a portion of the second surface of the substrate, the reflective material surrounding an aperture through which light exits the device;

wherein a portion of the substrate not covered by the reflective material is covered by a wavelength converting material.

18. The light emitting device of claim 17 wherein the wavelength converting material is a phosphor.