Light emitting devices with compact active regions

• US 6,900,474 B2
• Filed: 07/31/2003
• Issued: 05/31/2005
• Est. Priority Date: 12/20/2002
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Shen, Yu-Chen, Stockman, Stephen A., Misra, Mira S.
• Primary Examiner(s): Pham, Hoai
• Assistant Examiner(s): Farahani, Dana
• Application Number:
  US10/632,720
• Publication Number:
  US 20040119077A1
• Time in Patent Office: 670 Days
• Field of Search: 257/79, 257/80, 257/81, 257/82, 257/83, 257/84, 257/85, 257/86, 257/87, 257/88, 257/89, 257/90, 257/94, 257/98, 438/30
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/1403 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair

Abstract

A light emitting device includes a region of first conductivity type, a region of second conductivity type, an active region, and an electrode. The active region is disposed between the region of first conductivity type and the region of second conductivity type and the region of second conductivity type is disposed between the active region and the electrode. The active region has a total thickness less than or equal to about 0.25λ_n and has a portion located between about 0.6λ_n and 0.75λ_n from the electrode, where λ_n is the wavelength of light emitted by the active region in the region of second conductivity type. In some embodiments, the active region includes a plurality of clusters, with a portion of a first cluster located between about 0.6λ_n and 0.75λ_n from the electrode and a portion of a second cluster located between about 1.2λ_n and 1.35λ_n from the electrode.

Claims

1. A light emitting device comprising:

a region of first conductivity type;

a region of second conductivity type;

an active region disposed between the region of first conductivity type and the region of second conductivity type, the active region being capable of emitting light having a wavelength λ

_n in the region of second conductivity type; and

a surface reflective of the light emitted by the active region, wherein one of the region of first conductivity type and the region of second conductivity type is disposed between the active region and the reflective surface;

wherein the active region has a total thickness less than or equal to about 0.25λ

_n and wherein a portion of the active region is located between 0.6λ

_n and 0.75λ

_n from the reflective surface.

2. The light emitting device of claim 1 wherein the active region comprises two quantum well layers separated by a barrier layer.

3. The light emitting device of claim 2 wherein each of the quantum well layers has a thickness ranging between about 10 and about 60 angstroms, and wherein the barrier layer has a thickness ranging from about 50 to about 200 angstroms.

4. The light emitting device of claim 1 wherein the active region comprises three quantum well layers separated by two barrier layers.

5. The light emitting device of claim 1 wherein the active region has a total thickness less than or equal to about 0.15λ

_n.

6. The light emitting device of claim 1 wherein a physical center of the active region is located at a distance from the reflective surface corresponding to within 0.05λ

_n from a local maximum in extraction efficiency.

7. The light emitting device of claim 1 wherein a center of brightness of the active region is located at a distance from the reflective surface corresponding to within 0.05λ

_n from a local maximum in extraction efficiency.

8. The light emitting device of claim 1 wherein the reflective surface has a reflectivity greater than 80% for light emitted by the active region.

9. The light emitting device of claim 1 wherein the active region comprises at least one III-nitride layer.

10. The light emitting device of claim 1 wherein the active region comprises at least one III-phosphide layer.

11. The light emitting device of claim 1 wherein the reflective surface comprises silver.

12. The light emitting device of claim 1 wherein the reflective surface comprises gold.

13. The light emitting device of claim 1 wherein the reflective surface comprises aluminum.

14. The light emitting device of claim 1 wherein:

is a first electrode; and

the first electrode is electrically connected to the region of second conductivity type, the light emitting device further comprising;

a second electrode electrically connected to the region of first conductivity type; and

a submount electrically connected to the first and second electrodes.

15. The light emitting device of claim 14 further comprising:

a plurality of leads electrically connected to the submount; and

a lens overlying the active region.

16. The light emitting device of claim 1 wherein:

the portion of the active region located between 0.6λ

_n and 0.75λ

_n from the reflective surface comprises a first portion of the active region; and

a second portion of the active region is located between 1.2λ

_n and 1.35λ

_n from the reflective surface.

17. The light emitting device of claim 1 wherein the reflective surface is a surface of a metal electrode.

18. The light emitting device of claim 1 wherein the reflective surface is a surface of a distributed Bragg reflector.

19. A light emitting device comprising:

a region of first conductivity type;

a region of second conductivity type;

an active region disposed between the region of first conductivity type and the region of second conductivity type, the active region being capable of emitting light having a wavelength λ

_n in the region of second conductivity type; and

an electrode reflective of the light emitted by the active region, wherein the region of second conductivity type is disposed between the active region and the electrode;

wherein;

the active region comprises a first cluster and a second cluster;

a portion of the first cluster is located between 0.6λ

_n and 0.75λ

_n from a surface of the electrode; and

a portion of the second cluster is located between 1.2λ

_n and 1.35λ

_n from a surface of the electrode.

20. The light emitting device of claim 19 wherein each of the first cluster and the second cluster comprise a plurality of quantum wells separated by at least one barrier layer.

21. The light emitting device of claim 20 wherein a thickness of each of the first cluster and the second cluster is less than or equal to about 0.35λ

_n.

22. The light emitting device of claim 20 wherein a thickness of each of the first cluster and the second cluster is less than or equal to about 0.15λ

_n.

23. The light emitting device of claim 19 wherein the first cluster and the second cluster are separated by a barrier layer.

24. The light emitting device of claim 19 wherein the active region comprises at least one III-nitride layer.

25. The light emitting device of claim 19 wherein the active region comprises at least one III-phosphide layer.

26. A light emitting device comprising:

a region of first conductivity type;

a region of second conductivity type;

an active region disposed between the region of first conductivity type and the region of second conductivity type, the active region being capable of emitting light having a wavelength λ

_n in the region of second conductivity type; and

an electrode reflective of the light emitted by the active region, wherein the region of second conductivity type is disposed between the active region and the electrode;

wherein the active region has a total thickness less than or equal to about 0.25λ

_n and wherein a portion of the active region is located between 0.1λ

_n and 0.32λ

_n from a surface of the electrode.