Light emitting devices with compact active regions

• US 7,719,018 B2
• Filed: 05/27/2005
• Issued: 05/18/2010
• Est. Priority Date: 12/20/2002
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Misra, Mira S., Shen, Yu-Chen, Stockman, Stephen A.
• Primary Examiner(s): Monbleau; Davienne
• Assistant Examiner(s): REAMES, MATTHEW L
• Application Number:
  US11/139,325
• Publication Number:
  US 20050212005A1
• Time in Patent Office: 1,817 Days
• Field of Search: 257/98, 257/E33.012, 257/E33.008, 257/E33.072, 257/79
• 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 comprises a first cluster and a second cluster, each of the first and second clusters comprising at least two quantum well layers separated by a barrier layer;

each of the first and second clusters has a total thickness less than or equal to about 580 angstroms;

a portion of the first cluster is located between 0.6λ

_n and 0.75λ

_n from the reflective surface;

a portion of the second cluster is located between 1.1λ

_n and 1.4λ

_n from the reflective surface; and

the first and second clusters are separated by a semiconductor layer that is thicker than each barrier layer.

2. The light emitting device of claim 1 wherein each of the first and second clusters has a thickness less than about 320 angstroms.

3. The light emitting device of claim 1 wherein each of the first and second clusters comprises three quantum well layers separated by two barrier layers.

4. The light emitting device of claim 3 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.

5. The light emitting device of claim 2 wherein each of the first and second clusters comprises two quantum well layers separated by a barrier layer.

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

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

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

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

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

11. The light emitting device of claim 1 wherein a physical center of at least one of the first and second clusters is located at a distance from the reflective surface corresponding to within 0.05λ

_n from a local maximum in extraction efficiency.

12. The light emitting device of claim 1 wherein a center of brightness of at least one of the first and second clusters is located at a distance from the reflective surface corresponding to within 0.05λ

_n from a local maximum in extraction efficiency.