Light-emitting diode with planar omni-directional reflector

• US 20030111667A1
• Filed: 12/12/2002
• Published: 06/19/2003
• Est. Priority Date: 12/13/2001
• Status: Active Grant

• Current Assignee: Rensselaer Polytechnic Institute
• Original Assignee: Rensselaer Polytechnic Institute
• Inventors: Schubert, E. Fred
• Granted Patent: US 6,784,462 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/405 Reflective materials

Abstract

A high extraction efficiency, light-emitting diode having a reflective submount and methods for forming the LED. A light-emitting region is disposed between a top contact and a conductive holder. The region extends beyond an area underlying the top contact. An omni-directional reflector is disposed between the light-emitting region and the conductive holder. According to one embodiment, the reflector comprises one or more electrically conductive contacts configured to correspond to an area beyond the area underlying the top contact. According to one embodiment, the reflector comprises a dielectric layer having a refractive index of between about 1.10 and 2.25, contacts extending through the reflector, and a reflective conductive film.

Claims

1. A light-emitting diode comprising:

a top contact defining an area underlying the top contact;

a conductive holder;

a light-emitting region disposed between the top contact and the conductive holder and extending beyond the area underlying the top contact; and

an omni-directional reflector disposed between the light-emitting region and the conductive holder, the omni-directional reflector having one or more electrically conductive contacts configured to correspond to a region beyond the area underlying the top contact.

2. The light-emitting diode of claim 1 wherein the one or more electrically conductive contacts are disposed in a dielectric layer having a refractive index of between about 1.10 and 2.25.

3. The light-emitting diode of claim 2 wherein the dielectric layer comprises silicon dioxide.

4. The light-emitting diode of claim 2 wherein the dielectric layer comprises silicon nitride.

5. The light-emitting diode of claim 2 wherein the dielectric layer comprises magnesium fluoride.

6. The light-emitting diode of claim 2 wherein the dielectric layer has a thickness proportional to approximately a quarter-wavelength of the extracted light and inversely proportional to its refractive index.

7. The light-emitting diode of claim 2 wherein the one or more electrically conductive contacts is a pattern of ohmic contacts covering less than half of the cross-sectional area of the dielectric layer.

8. The light-emitting diode of claim 7 wherein the pattern of ohmic contacts covers less than one-tenth of the cross-sectional area of the dielectric layer.

9. The light-emitting diode of claim 2 wherein the omni-directional reflector comprises an insulating layer having a refractive index of between about 1.10 and 2.25 underlying the top contact and a single conductive contact having a refractive index of between about 1.10 and 2.25 underlying an area beyond the periphery of the top contact.

10. The light-emitting diode of claim 9 wherein the insulating layer comprises silicon dioxide.

11. The light-emitting diode of claim 9 wherein the conductive contact comprises indium-tin-oxide.

12. A light-emitting diode comprising:

an active region having two opposite-conductivity-type confinement layers with a light-emitting region disposed between the layers; and

an omni-directional reflector proximate a first one of the confinement layers opposite the light-emitting region.

13. The light-emitting diode of claim 12 further comprising a window disposed adjacent each confinement layer and opposite the light emitting region.

14. The light-emitting diode of claim 13 wherein the light-emitting region comprises a multiple quantum well structure, the confinement layers comprise AlGaInP doped with a p-type dopant and AlGaInP doped with a n-type dopant, and at least one of the windows comprise doped AlGaInP.

15. The light-emitting diode of claim 14 wherein one of the windows comprises essentially GaP.

16. The light-emitting diode of claim 15 wherein the top window comprises GaP.

17. The light-emitting diode of claim 15 wherein the bottom window comprises GaP.

18. The light-emitting diode of claim 14 wherein the top and bottom windows have a thickness of between about 1 and 25 microns.

19. The light-emitting diode of claim 14 wherein the top window has a thickness of between about 5 and 20 microns and the bottom window has a thickness of between about 1 and 15 microns.

20. The light-emitting diode of claim 12 wherein the omni-directional reflector comprises a dielectric layer having a low refractive index, an array of ohmic contacts extending through the dielectric layer, and a metal layer disposed proximate the dielectric layer opposite the light-emitting region.

21. The light-emitting diode of claim 20 wherein the array of ohmic contacts is disposed in a pattern underlying an area beyond the periphery of the top contact.

22. A method for forming a light-emitting diode comprising the steps of:

forming epitaxial layers on a substrate, the epitaxial layers comprising a light-emitting region;

forming a top contact over the epitaxial layers;

attaching a temporary holder to the top contact and the epitaxial layers;

removing the substrate;

forming an omni-directional reflector on the epitaxial layers;

attaching a conductive holder to the omni-directional reflector; and

removing the temporary holder.

23. The method of claim 22 wherein the epitaxial layers further comprise top and bottom confinement layers and top and bottom windows.

24. The method of claim 23 wherein the light-emitting region, the top and bottom confinement layers, and at least one of the top and bottom windows comprise aluminum gallium indium phosphide.

25. The method of claim 24 wherein one of the top and bottom windows comprises gallium phosphide.

26. The method of claim 22 wherein the omni-directional reflector comprises a pattern of ohmic contacts extending through a dielectric layer and underlying an area beyond the periphery of the top contact.

27. The method of claim 26 wherein the omni-directional reflector is formed by depositing a blanket dielectric layer with an index of refraction of between about 1.10 and 2.25 on the epitaxial layers, patterning the dielectric layer to form openings in the dielectric layer, and forming ohmic contacts in the openings.

28. The method of claim 26 wherein the omni-directional reflector is created by forming a blanket conductive layer, patterning the conductive layer to form one or more conductive contacts in a pattern underlying an area beyond the periphery of the top contact, and forming a dielectric layer with an index of refraction of between about 1.10 and 2.25 in areas not having conductive contacts.

29. A method for forming a light-emitting diode comprising the steps of:

forming epitaxial layers on a substrate, the epitaxial layers comprising a light-emitting region;

forming an omni-directional reflector on the epitaxial layers;

attaching a conductive holder to the omni-directional reflector;

removing the substrate; and

forming a top contact on the epitaxial layers opposite the conductive holder.