III-nitride light-emitting device with increased light generating capability

• US 20020171087A1
• Filed: 03/29/2002
• Published: 11/21/2002
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Kish,, Fred A. Jr., Krames, Michael R., Wierer, Jonathan J. Jr., Steigerwald, Daniel A., Tan, Tun S., Rajkomar, Pradeep
• Granted Patent: US 6,521,914 B2
• Time in Patent Office: Days
• US Class Current: 257/81
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• 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 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05572 the external layer extending out of an opening
• CPC Class Codes: H01L 2224/06051 Bonding areas having different shapes
• CPC Class Codes: H01L 2224/14 of a plurality of bump connectors
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/06 of a plurality of bonding areas
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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 33/405 Reflective materials
• 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
• CPC Class Codes: H01L 33/641 characterized by the materials
• CPC Class Codes: H01L 33/647 the elements conducting electric current to or from the semiconductor body

Abstract

The present invention is an inverted III-nitride light-emitting device (LED)) with enhanced total light generating capability. A large area device has an n-electrode that interposes the p-electrode metallization to provide low series resistance. The p-electrode metallization is opaque, highly reflective, and provides excellent current spreading. The p-electrode at the peak emission wavelength of the LED active region absorbs less than 25% of incident light per pass. A submount may be used to provide electrical and thermal connection between the LED die and the package. The submount material may be Si to provide electronic functionality such as voltage-compliance limiting operation. The entire device, including the LED-submount interface, is designed for low thermal resistance to allow for high current density operation. Finally, the device may include a high-refractive-index (n>1.8) superstrate.

Claims

1. A light-emitting device comprising:

a heterostructure of III-nitride material, having a first light emitting unit that contains an active region, having an n and a p contact layer;

an opaque p electrode, attached to the p contact layer;

an n electrode, attached to the n contact layer, interposing the p electrode; and

a p and an n solder interface, the p-solder interface affixed to the p-electrode and the n-solder interface affixed to the n-electrode;

wherein the lateral cross-sectional area of the solder interfaces is at least 15% of the p electrode area.

2. A light-emitting device, as defined in claim 1, further including a dielectric material covering a portion of one of the p and n solder interfaces.

3. A light-emitting device, as defined in claim 1, further including a dielectric material covering the perimeter of one of the p and n solder interfaces.

4. A light-emitting device, as defined in claim 1, further including a barrier layer interposing the one of the p and n-electrodes and the corresponding solder interface.

5. A light-emitting device, as defined in claim 1, further including an intermetal dielectric material covering portions of one of the p and n electrodes.

6. A light-emitting device, as defined in claim 1, wherein the active region area is greater than 0.16 mm².

7. A light-emitting device, as defined in claim 1, wherein the p-electrode has an absorption less than 25%.

8. A light-emitting device, as defined in claim 7, wherein the p-electrode is comprised of Ni and Ag.

9. A light-emitting device, as defined in claim 7, wherein the p-electrode is comprised of Au, NiO_x, and Al.

10. A light-emitting device, as defined in claim 1, wherein at least one of the layers comprising the heterostructure is textured.

11. A light-emitting device, as defined in claim 1, wherein the specific contact resistivity of the p-electrode is less than 10⁻

2Ω

cm².

12. A light-emitting device, as defined in claim 1, further comprising a submount electrically connected to the heterostructure via the solder interfaces.

13. A light-emitting device, as defined in claim 12, wherein the submount is silicon.

14. A light-emitting device, as defined in claim 12, wherein the submount includes a circuit consisting of at least one diode electrically connected in anti-parallel with the light-emitting device p-n junction.

15. A light-emitting device, as defined in claim 12, wherein the submount includes a circuit consisting of at least one photo-diode in the path of light emitted from the light-emitting device.

16. A light-emitting device, as defined in claim 12, wherein the submount has a shape selected from a group including hexagons, circles, squares, and octagons.

17. A light-emitting device, as defined in claim 12, further comprising:

a second light emitting unit positioned on the III-nitride heterostructure; and

the III-nitride heterostructure further including a trench;

wherein the first and second light emitting units are positioned on opposing sides of the trench and are electrically connected in series.

19. A light-emitting device, as defined in claim 18, wherein the superstrate has an absorption coefficient less than 3 cm⁻

1 at the peak emission wavelength.

20. A light-emitting device, as defined in claim 18, wherein the p-electrode has an absorption less than 25%.

21. A light-emitting device, as defined in claim 18, wherein at least one of the layers comprising the heterostructure is textured.

22. A light-emitting device, as defined in claim 18, wherein the superstrate is selected from a group that includes SiC, ZnO, YAG, ZnSe, ZnS, zirconia, diamond, and CdS.

23. A light-emitting device, as defined in claim 22, wherein the superstrate is SiC and has a resistivity greater than 0.5Ω

cm.

24. A light-emitting device, as defined in claim 18, wherein at least one surface of the superstrate is roughened.

25. A light-emitting device, as defined in claim 18, wherein a top surface area of the superstrate is larger than a bottom surface area of the superstrate.

27. A light-emitting device, as defined in claim 26, wherein the distance between the center of the active region and the p-electrode is approximately one quarter-wavelength of the peak emission wavelength.

28. A light-emitting device, as defined in claim 27, wherein the distance between the center of the active region and the p-electrode is approximately 500 Å

.

18. A light-emitting device comprising:

a heterostructure of III-nitride materials, containing an active region having a peak emission wavelength, including an n contact layer and a p contact layer;

a p and an n electrode, the p electrode being attached to the p contact layer, the n electrode being attached to the n contact layer; and

a superstrate, having a refractive index greater than 1.8, attached to the heterostructure.

26. A light-emitting device comprising:

a heterostructure of III-nitride material, containing an active region having a peak emission wavelength, including an n contact layer and a p contact layer;

a p and an n electrode, the p-electrode having an absorption less than 25% and being attached to the p contact layer, the n electrode being attached to the n contact layer; and

an active region having a center positioned relative to the p electrode at a distance of approximately an odd multiple of quarter-wavelengths of the peak emission wavelength.