Light emitting diode device comprising a luminescent substrate that performs phosphor conversion

• US 6,630,691 B1
• Filed: 09/27/1999
• Issued: 10/07/2003
• Est. Priority Date: 09/27/1999
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Vanderwater, David A., Mueller-Mach, Regina B., Mueller, Gerd O.
• Primary Examiner(s): Tran, Minh Loan
• Assistant Examiner(s): Dickey, Thomas L
• Application Number:
  US09/407,231
• Time in Patent Office: 1,471 Days
• Field of Search: 257/94, 257/98-103, 257/13-18, 257/76-82, 257/20, 257/22, 257/84, 257/95, 257/96, 313/499-504, 313/456-472, 313/505, 313/473, 372/10-14, 372/66-75
• US Class Current: 257/84
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/50 Wavelength conversion elements

Abstract

The present invention provides an LED device comprising a phosphor-converting substrate that converts primary light emitted by the LED, which is blue light, into one or more other wavelengths of light, which then combine with unconverted primary light to produce white light. The substrate is a single crystal phosphor having desired luminescent properties. The single crystal phosphor has the necessary lattice structure to promote single crystalline growth of the light-emitting structure of the LED device. Moreover, the thermo-mechanical properties of the substrate are such that the introduction of excessive strain or cracks in the epitaxial films of the LED device is prevented. The characteristics of the substrate, i.e., the dopant concentration and thickness, are capable of being precisely controlled and tested before the LED device is fabricated so that the fraction of primary light that passes through the substrate without being converted is predictable and controllable. Likewise, the fraction of primary light that is converted by the substrate into one or more other wavelengths is predictable and controllable. By precisely controlling these fractions, phosphor-converted LED devices can be achieved that produce uniform, high-quality white light.

Claims

1. A light emitting diode device for generating white light, the light emitting diode device comprising:

a light emitting structure, the light emitting structure emitting primary radiation of a particular wavelength when driven; and

a light-transmissive substrate comprising a Yttrium-Aluminum-oxide compound, at least a portion of the primary radiation emitted from the light emitting structure propagating into the substrate, the substrate being doped in such a manner that at least a portion of the primary radiation propagating into the substrate is converted into radiation of one or more other wavelengths, and wherein a portion of the primary radiation emitted by the light emitting structure is not converted into said radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation combines with said radiation of one or more other wavelengths to produce white light.

2. The light emitting diode device of claim 1, further comprising:

a reflective surface, the light-transmissive substrate being sandwiched between the light emitting structure and the reflective surface, wherein substantially all of the primary radiation propagating into the substrate is converted into the radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation corresponds to primary radiation emitted by the light emitting structure in a direction away from the substrate, the reflective surface reflecting the radiation of one or more other wavelengths through the substrate and the light emitting structure, the reflected radiation and the unconverted primary radiation combining to form white light.

3. The light emitting diode device of claim 1, further comprising:

a reflective electrode disposed on a first surface of the light emitting structure, wherein any primary radiation emitted by the light emitting structure that impinges on the reflective electrode is reflected by the reflective electrode toward the light emitting structure such that the reflected radiation is directed toward the substrate.

4. The light emitting diode device of claim 1, wherein the primary radiation is blue light.

5. The light emitting diode device of claim 1, wherein said light-transmissive substrate is doped with at least one of Cerium, Praseodymium, Holmium, Ytterbium, and Europium.

6. The light emitting diode device of claim 1, wherein the primary radiation includes ultraviolet light.

7. A light emitting diode device for generating white light, the light emitting diode device comprising:

a light emitting structure, the light emitting structure emitting primary radiation of a particular wavelength when driven; and

a light-transmissive substrate comprising an Aluminum-rare earth ion-oxide compound, at least a portion of the primary radiation emitted from the light emitting structure propagating into the substrate, the substrate being doped in such a manner that at least a portion of the primary radiation propagating into the substrate is converted into radiation of one or more other wavelengths, and wherein a portion of the primary radiation emitted by the light emitting structure is not converted into said radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation combines with said radiation of one or more other wavelengths to produce white light.

8. The light emitting diode device of claim 7, further comprising:

a reflective surface, the light-transmissive substrate being sandwiched between the light emitting structure and the reflective surface, wherein substantially all of the primary radiation propagating into the substrate is converted into the radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation corresponds to primary radiation emitted by the light emitting structure in a direction away from the substrate, the reflective surface reflecting the radiation of one or more other wavelengths through the substrate and the light emitting structure, the reflected radiation and the unconverted primary radiation combining to form white light.

9. The light emitting diode device of claim 7, further comprising:

a reflective electrode disposed on a first surface of the light emitting structure, wherein any primary radiation emitted by the light emitting structure that impinges on the reflective electrode is reflected by the reflective electrode toward the light emitting structure such that the reflected radiation is directed toward the substrate.

10. The light emitting diode device of claim 7, wherein at least a portion of said radiation of one or more other wavelengths is yellow light, and wherein the yellow light combines with the unconverted primary radiation to produce white light.

11. The light emitting diode device of claim 7, wherein the primary radiation is blue light.

12. The light emitting diode device of claim 7, wherein the single crystal Yttrium Aluminum-Garnet compound is doped with Cerium to produce a compound chemically defined as Y₃Al₅O₁₂:

Ce³⁺.

13. The light emitting diode device of claim 7, wherein the single crystal Yttrium Aluminum-Garnet compound is doped with Holmium to produce a compound chemically defined as Y₃Al₅O₁₂:

Ho³⁺.

14. The light emitting diode device of claim 7, wherein the single crystal Yttrium Aluminum-Garnet (Y₃Al₅O₁₂) compound is doped with Praseodymium to produce a compound chemically defined as Y₃Al₅O₁₂:

Pr³⁺.

15. The light emitting diode device of claim 7, wherein the substrate further comprises a Yttrium-Aluminum-rare earth ion-oxide.

16. The light emitting diode device of claim 15, wherein said Yttrium-Aluminum-rare earth ion-oxide is Yttrium-Aluminum-Lutethium-Oxide.

17. The light emitting diode device of claim 15, wherein said Yttrium-Aluminum-rare earth ion-oxide is Yttrium-Aluminum-Lutethium-Gallium-Oxide.

18. The light emitting diode device of claim 7, wherein said light-transmissive substrate is doped with at least one of Cerium, Praseodymium, Holmium, Ytterbium, and Europium.

19. The light emitting diode device of claim 7, wherein the primary radiation includes ultraviolet light.

20. A light emitting diode device for generating white light, the light emitting diode device comprising:

a light emitting structure, the light emitting structure emitting primary radiation of a particular wavelength when driven; and

a light-transmissive substrate comprised of a non-garnet Yttrium-Aluminum-Oxide, at least a portion of the primary radiation emitted from the light emitting structure propagating into the substrate, the substrate being doped in such a manner that at least a portion of the primary radiation propagating into the substrate is converted into radiation of one or more other wavelengths, and wherein a portion of the primary radiation emitted by the light emitting structure is not converted into said radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation combines with said radiation of one or more other wavelengths to produce white light.

21. The light emitting diode device of claim 20, wherein the light-transmissive substrate comprises monoklinic YAlO.

22. The light emitting diode of claim 20, wherein the light-transmissive substrate comprises YAlO-perovskite.

23. The light emitting diode device of claim 20, wherein said light-transmissive substrate is doped with at least one of Cerium, Praseodymium, Holmium, Ytterbium, and Europium.

24. A light emitting diode device for generating white light, the light emitting diode device comprising:

a light emitting structure, the light emitting structure emitting primary radiation of a particular wavelength when driven; and

a light-transmissive substrate comprised of an Aluminum-rare earth ion-oxide compound, at least a portion of the primary radiation emitted from the light emitting structure propagating into the substrate, the substrate being doped in such a manner that at least a portion of the primary radiation propagating into the substrate is converted into radiation of one or more other wavelengths, and wherein a portion of the primary radiation emitted by the light emitting structure is not converted into said radiation of one or more other wavelengths, and wherein the unconverted portion of the primary radiation combines with said radiation of one or more other wavelengths to produce white light.

25. The light emitting diode device of claim 24, wherein the substrate comprises a Yttrium-Aluminum-rare earth ion-oxide.

26. The light emitting diode device of claim 25, wherein said Yttrium-Aluminum-rare earth ion-oxide.

27. The light emitting diode device of claim 25, wherein said Yttrium-Aluminum-rare earth ion-oxide is Yttrium-Aluminum-Lutethium-Gallium-oxide.

28. The light emitting diode device of claim 25, wherein the primary radiation is blue light.

29. The light emitting diode device of claim 25, wherein the primary radiation includes ultraviolet light.

30. The light emitting diode device of claim 25, wherein the light-transmissive substrate is doped with at least one of Cerium, Praseodymium, Holmium, Ytterbium, and Europium.