High efficacy white LED

• US 8,288,942 B2
• Filed: 09/15/2005
• Issued: 10/16/2012
• Est. Priority Date: 12/28/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James
• Primary Examiner(s): Green, Tracie Y
• Application Number:
  US11/227,667
• Publication Number:
  US 20060138937A1
• Time in Patent Office: 2,588 Days
• Field of Search: 313498-512, 257/40, 257/72, 257 98-100, 257642-643, 257/759
• US Class Current: 313/512
• CPC Class Codes: F21K 9/68 Details of reflectors forming part of the light source
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A white light emitting solid-state lamp is disclosed having an output of at least 75 lumens per watt at 20 milliamps drive current. The lamp includes a light emitting diode, an encapsulant, and a header. The diode includes a conductive silicon carbide substrate for electrical contact and a Group III nitride active portion on the silicon carbide substrate for generating desired frequency photons under the application of current across the diode. The header includes a reflective cup for supporting the diode and for providing electrical contact to the diode and to the active portion. The encapsulant includes a phosphor, present in at least portions of the encapsulant for generating responsive frequencies when the phosphor is excited by the frequencies emitted by the diode.

Claims

1. A light emitting solid state lamp comprising:

a light emitting diode (LED) that emits photons having frequencies selected from the group consisting of the ultraviolet, violet and blue portions of the electromagnetic spectrum, an encapsulant, and a header;

said LED comprising a Group III nitride active portion for generating desired frequency photons under the application of current across said LED, wherein said LED is vertically oriented;

said header comprising a reflective cup for supporting said LED and for providing electrical contact to said diode LED and to said active portion;

an ohmic contact to said LED with said ohmic contact being in electrical and direct physical contact with said header;

said encapsulant comprising a phosphor, said encapsulant comprising a plurality of portions wherein said phosphor is present in at least one of said portions of said encapsulant that emits responsive frequencies in the yellow portion of the visible spectrum when excited by frequencies emitted from the group consisting of the ultraviolet, violet and blue portions of the electromagnetic spectrum emitted by said LED, wherein a substantially transparent first portion of said encapsulant partially fills said reflective cup and covers said LED and a second portion of said encapsulant comprises said phosphor and is on said first portion.

2. A solid state lamp according to claim 1 with an output of at least 80 lumens per watt at 20 milliamps drive current.

3. A solid state lamp according to claim 1 with an output of at least 85 lumens per watt at 20 milliamps drive current.

4. A solid state lamp according to claim 1 further comprising:

a conductive silicon carbide substrate comprising a single polytype;

at least one p-type Group III nitride layer on said substrate; and

at least one n-type Group III nitride layer on said substrate in a vertical orientation.

5. A solid state lamp according to claim 4 wherein said ohmic contact is in contact with one of said Group III nitride layers.

6. A solid state lamp according to claim 1 wherein said reflective cup includes a silver coating for maximizing light extraction from said lamp.

7. A solid state lamp according to claim 1 wherein said encapsulant comprises an epoxy resin.

8. A solid state lamp according to claim 1 wherein said phosphor comprises cerium yttrium aluminum garnet.

9. A solid state lamp according to claim 1 comprising at least one p-type Group III nitride layer and an ohmic contact to said p-type layer, said ohmic contact having an average thickness of between about 1 and 250 A.

10. A solid state lamp according to claim 9 wherein said ohmic contact has an average thickness of between about 1 and 10 A.

11. A lamp according to claim 1 wherein said LED has a total dimension between and including any ohmic contacts of no more than 250 μ

m.

12. A lamp according to claim 1 wherein said LED has a total dimension between and including any ohmic contacts of no more than 100 μ

m.

16. A solid state lamp according to claim 1 with an output of at least 75 lumens per watt at 20 milliamps drive current within a ccx of 0.32-0.37 and a ccy of 0.31-0.39 on the CIE diagram.

18. A solid state lamp according to claim 1, wherein said LED is at least 900 μ

m×

900 μ

m, with a quantum efficiency of at least 31% when operating at no more than 350 mA.

19. A solid state lamp according to claim 1, wherein said LED is at least 300 μ

m×

300 μ

m, with a quantum efficiency of at least 44% when operating at no more than 20 mA.

22. A solid state lamp according to claim 1, wherein the reflective cup comprises a functional shape that maximizes an extraction of light from the LED.

23. A solid state lamp according to claim 1, wherein the reflective cup comprises a frustoconical shape.

24. A solid state lamp according to claim 23, wherein the frustoconical shape comprises the reflective cup including a floor facing a parallel and larger opening and a slanted wall between the floor and the opening.

13. A light emitting solid state lamp comprising:

a light emitting LED that emits photons having frequencies selected from the group consisting of the ultraviolet, violet and blue portions of the electromagnetic spectrum, an encapsulant, and a header;

said LED comprising a conductive substrate for electrical contact and is vertically oriented;

a Group III nitride active portion on said substrate for generating desired frequency photons under the application of current across said LED;

said header comprising a reflective cup for supporting said LED and for providing electrical contact to said LED and to said active portion, said header in direct contact with said LED;

said encapsulant comprising a phosphor, said encapsulant comprising at least a first portion and a second portion wherein said phosphor is present in at least one of said portions of said encapsulant that emits responsive frequencies in the yellow portion of the visible spectrum when excited by frequencies emitted from the group consisting of the ultraviolet, violet and blue portions of the electromagnetic spectrum emitted by said LED, wherein said first portion is substantially transparent, partially fills said reflective cup, and covers said LED, and said second portion comprises said phosphor and is on said first portion.

14. A light emitting solid state lamp according to claim 13 wherein said Group III nitride active portion includes at least one p-type and one n-type layer on said substrate for generating desired frequency photons under the application of current across said LED;

and

said p-type layer is positioned adjacent said header.

15. A light emitting solid state lamp according to claim 13 wherein said substrate includes light extraction features.

17. A light emitting solid state lamp according to claim 13 with an output of at least 75 lumens per watt at 20 milliamps drive current within a ccx of 0.32-0.37 and a ccy of 0.31-0.39 on the CIE diagram.

20. A light emitting solid state lamp according to claim 13, wherein said LED is at least 900 μ

m×

900 μ

m, with a quantum efficiency of at least 31% when operating at no more than 350 mA.

21. A light emitting solid state lamp according to claim 13, wherein said LED is at least 300 μ

m×

300 μ

m, with a quantum efficiency of at least 44% when operating at no more than 20 mA.

25. A light emitting solid state lamp according to claim 13, wherein the reflective cup comprises a functional shape that maximizes an extraction of light from the LED.

26. A light emitting solid state lamp according to claim 13, wherein the reflective cup comprises a frustoconical shape.

27. A light emitting solid state lamp according to claim 26, wherein the frustoconical shape comprises the reflective cup including a floor facing a parallel and larger opening and a slanted wall between the floor and the opening.