High voltage low current surface emitting LED

• US 8,530,921 B2
• Filed: 07/25/2011
• Issued: 09/10/2013
• Est. Priority Date: 04/06/2009
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Heikman, Sten
• Primary Examiner(s): Lebentritt, Michael
• Application Number:
  US13/190,126
• Publication Number:
  US 20110278608A1
• Time in Patent Office: 778 Days
• Field of Search: 257/79, 257 88- 99, 257/E21.001, 257/2, 257/499, 257/27.121, 257/33.001, 257/5, 257/56, 257/61, 257/66
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate

Abstract

A monolithic LED chip is disclosed comprising a plurality of junctions or sub-LEDs (“sub-LEDs”) mounted on a submount. The sub-LEDs are serially interconnected such that the voltage necessary to drive the sub-LEDs is dependent on the number of serially interconnected sub-LEDs and the junction voltage of the sub-LEDs. Methods for fabricating a monolithic LED chip are also disclosed with one method comprising providing a single junction LED on a submount and separating the single junction LED into a plurality of sub-LEDs. The sub-LEDs are then serially interconnected such that the voltage necessary to drive the sub-LEDs is dependent on the number of the serially interconnected sub-LEDs and the junction voltage of the sub-LEDs.

Claims

1. A monolithic LED chip, comprising a plurality of serially-interconnected sub-LEDs bonded to a submount by a common bond layer that is not electrically connected to the sub-LEDs.

2. The LED chip of claim 1, further comprising electrically conductive features that are disposed on a side of the common bond layer opposite the submount and that serially interconnect said sub-LEDs.

3. The LED chip of claim 2, wherein said electrically conductive features comprise bottom contacts and connector traces.

4. The LED chip of claim 2, wherein said electrically conductive features comprise wire bond pads.

5. The LED chip of claim 2, further comprising electrically insulating features that insulate said electrically conductive features from other portions of said LED chip to prevent shorting of signals on said electrically conductive features.

6. The LED chip of claim 1, wherein the alignment tolerance between said sub-LEDs is less than 5 microns.

7. The LED chip of claim 1, wherein the alignment tolerance between said sub-LEDs is less than 2 microns.

8. The LED chip of claim 1, wherein said sub-LEDs are formed from a single junction LED.

9. The LED chip of claim 8, wherein said sub-LEDs are formed from a single junction LED by removing portions of said single junction LED.

10. The LED chip of claim 8, wherein said sub-LEDs are formed from a single junction LED by isolation implants.

11. The LED chip of claim 8, wherein the active area utilization ratio is greater than 50%.

12. The LED chip of claim 8, wherein the active area utilization ratio is greater than 75%.

13. The LED chip of claim 1, further comprising an insulating layer between said sub-LEDs and substrate.

14. The LED chip of claim 1, further comprising an insulator layer between said sub-LEDs and said submount.

15. The LED chip of claim 14, wherein said insulator layer has a thickness to tolerate the voltage driving said sub-LEDs.

16. The LED chip of claim 1, emitting a white light from said sub-LEDs.

17. The LED chip of claim 1, emitting down converted light from said sub-LEDs.

18. The LED chip of claim 1, wherein the remaining ones of said serially connected sub-LEDs are capable of emitting light in response to said drive voltage when one of said sub-LEDs fail.

19. The LED chip of claim 2, wherein the electrically conductive features comprise at least one conductive trace contacting a top surface of a bottom contact of a first one of the sub-LEDs and a top surface of a second one of the sub-LEDs.

20. The LED chip of claim 19, wherein the at least one conductive trace has a portion that conforms to a side surface of the second one of the sub-LEDs.

21. The LED chip of claim 20, further comprising at least one insulating layer insulating the side surface from the at least one conductive trace.

22. The LED chip of claim 21, wherein the at least one insulating layer fills a gap between bottom contacts of the first and second ones of the sub-LEDs.

23. The LED chip of claim 19, further comprising at least one insulating layer insulating at least one of the first and second ones of the sub-LEDs from the at least one conductive trace.

24. The LED chip of claim 23, wherein the at least one insulating layer fills a gap between bottom contacts of the first and second ones of the sub-LEDs.