High-powered light emitting device with improved thermal properties

• US 20040160173A1
• Filed: 02/19/2003
• Published: 08/19/2004
• Est. Priority Date: 02/19/2003
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Martin, Paul S., Shen, Yu-Chen, Steigerwald, Daniel A.
• Granted Patent: US 6,977,396 B2
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/05124 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05139 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/05144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05147 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• CPC Class Codes: H01L 2224/131 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/16237 the bump connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/16 of an individual bump connector
• CPC Class Codes: H01L 24/17 of a plurality of bump connectors
• 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 2924/01012 Magnesium [Mg]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12041 : LED
• CPC Class Codes: H01L 33/20 : with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 : with a particular shape
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

A light emitting device includes a first semiconductor layer of a first conductivity type, an active region, and a second semiconductor layer of a second conductivity type. First and second contacts are connected to the first and second semiconductor layers. In some embodiments at least one of the first and second contacts has a thickness greater than 3.5 microns. In some embodiments, a first heat extraction layer is connected to one of the first and second contacts. In some embodiments, one of the first and second contacts is connected to a submount by a solder interconnect having a length greater than a width. In some embodiments, an underfill is disposed between a submount and one of the first and second interconnects.

Claims

1. A light emitting device comprising:

a first semiconductor layer of a first conductivity type;

an active region overlying the first semiconductor layer, wherein the active region is capable of emitting light;

a second semiconductor layer of a second conductivity type overlying the active region;

a first contact connected to the first semiconductor layer; and

a second contact connected to the second semiconductor layer;

wherein at least one of the first contact and the second contact has a thickness greater than 3.5 microns.

2. The device of claim 1 wherein the first semiconductor layer, active region, and second semiconductor layer are III-nitride layers, and the first and second contacts are fonned on a same side of the device.

3. The device of claim 1 wherein at least one of the first contact and the second contact comprise a plurality of layers of different composition, wherein the total thickness of the plurality of layers is greater than 3.5 microns.

4. The device of claim 1 wherein at least one of the first contact and the second contact has a thickness greater than ten microns.

5. The device of claim 1 wherein both the first and second contacts have a thickness greater than 3.5 microns.

6. The device of claim 1 wherein at least one of the first contact and the second contact comprises at least one metal selected from the group consisting of Ag, Al, Au, and Cu.

7. The device of claim 1 further comprising a substrate underlying the first semiconductor layer, wherein the substrate is SiC.

8. The device of claim 1 wherein at least one of the first contact and the second contact comprises a first heat extraction layer, wherein the first heat extraction layer has a thickness greater than 0.2 micron.

9. The device of claim 8 wherein the first heat extraction layer has a thickness greater than 3.5 microns.

10. The device of claim 8 wherein the first heat extraction layer comprises at least one material selected from the group consisting of Cu, Al, Au, Ni, V, and metal alloys.

11. The device of claim 8 wherein the first heat extraction layer has an area greater than about 20 percent of an area of at least one of the first semiconductor layer and the second semiconductor layer.

12. The device of claim 1 wherein the device has an area greater than or equal to one square millimeter.

13. The device of claim 1 wherein the device has an area less than or equal to one square millimeter.

14. The device of claim 1 wherein the device has a thermal resistance per area less than about 10 K/W-mm² when operated at a current density of at least 143 A/cm².

15. The device of claim 1 further comprising:

a submount; and

at least one solder interconnect disposed between the submount and one of the first and second contacts, wherein a length of the solder interconnect is longer than a width of the solder interconnect.

16. The device of claim 15 wherein the solder interconnect comprises at least one material selected from the group consisting of In, Sn, metal alloys, and Ag_xIn_100-x, wherein x is between zero and 100.

17. The device of claim 1 further comprising:

a growth substrate, wherein the first semiconductor layer, second semiconductor layer and active region are formed on the growth substrate;

a submount;

an interconnect disposed between the submount one of the first and second contacts, wherein the interconnect physically and electrically connects the submount to one of the first and second contacts; and

an underfill disposed between the submount and the growth substrate.

18. The device of claim 17 wherein the underfill is selected from the group consisting of diamond, boron nitride, and titanium oxide.

19. The device of claim 17 wherein the underfill has a thermal conductivity greater than about 3 W/m-K.

20. The device of claim 17 wherein the underfill fills an area greater than about 70 percent of an area of the first semiconductor layer.

21. The device of claim 1 further comprising:

a first lead electrically connected to the first contact;

a second lead electrically connected to the second contact; and

a cover disposed on a side of the first semiconductor layer opposite the active region.

22. A method of operating a light emitting device, the method comprising:

forming a first semiconductor layer of a first conductivity type;

forming an active region overlying the first semiconductor layer;

forming a second semiconductor layer of a second conductivity type overlying the active region;

selecting at least one of an area, thickness, and material of one of a first contact and a second contact to reduce a temperature gradient within the device during operation to less than about 30 K/mm;

forming the first contact electrically connected to the first semiconductor layer;

forming a second contact electrically connected to the second semiconductor layer; and

operating the device at a current density greater than 143 A/cm²;

wherein a maximum temperature gradient within the device is less than 30 K/mm during operation.

23. The method of claim 22 further comprising selecting at least one of an area, thickness, and material of one of a first contact and a second contact to reduce a thermal resistance per area of the device, defined as a change in temperature divided by a corresponding change in power and area, to below 10 K/W-mm².

24. The method of claim 22 further comprising forming at least one heat extraction layer electrically connected to one of the first contact and the second contact.

25. The method of claim 22 further comprising attaching one of the first contact and the second contact to a submount by a solder interconnect having a length longer than a width.

26. The method of claim 22 further comprising:

attaching one of the first contact and the second contact to a submount; and

providing an underfill in a space between the submount and one of the first contact and the second contact.

27. A light emitting device comprising:

a substrate;

a first semiconductor layer of a first conductivity type overlying the substrate;

an active region overlying the first semiconductor layer, wherein the active region is capable of emitting light;

a second semiconductor layer of a second conductivity type overlying the active region;

a first contact connected to the first semiconductor layer; and

a second contact connected to the second semiconductor layer, the second contact comprising a plurality of layers including a heat extraction layer, the second contact having a thickness greater than 3.5 microns;

a submount;

an interconnect disposed between the submount and one of the first and second contacts, wherein the interconnect physically and electrically connects the submount to one of the first and second contacts and wherein the interconnect has a substantially rectangular vertical cross section; and

an underfill disposed between the submount and the substrate.

28. The device of claim 27 wherein the underfill substantially surrounds the interconnect.

29. The device of claim 27 wherein the interconnect comprises a solder bar.