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

• US 20020070386A1
• Filed: 02/07/2002
• Published: 06/13/2002
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Agilent Technologies Europe BV (Agilent Technologies, Inc.)
• Inventors: Krames, Michael R., Kish, Fred A. Jr., Wierer, Jonathan J. Jr., Steigerwald, Daniel A., Tan, Tun S., Rajkomar, Pradeep
• Granted Patent: US 6,844,571 B2
• Time in Patent Office: Days
• US Class Current: 257/94
• 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 materials comprising an active region having a peak emission wavelength, an n-layer, and a p-layer;

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

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

2. A light-emitting device, as defined in claim 1, wherein the superstrate has an absorption coefficient less than 3 cm⁻

1 at the peak emission wavelength.

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

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

5. A light-emitting device, as defined in claim 1, wherein the superstrate is selected from a group that includes SiC, ZnO, YAG, ZnSe, ZnS, zirconia, diamond, and CdS.

6. A light-emitting device, as defined in claim 5, wherein the superstrate is SiC and has a resistivity greater than 0.5 Ω

cm.

7. A light-emitting device, as defined in claim 1, wherein at least one surface of the superstrate is roughened.

8. A light-emitting device, as defined in claim 1, wherein a top surface area of the superstrate is larger than a bottom surface area of the superstrate.

9. A light-emitting device, as defined in claim 1, wherein a portion of the p-electrode interposes portions of the n-electrode.

10. A light-emitting device, as defined in claim 1, wherein the p-electrode comprises Au/NiO_x/Al.

11. A light-emitting device, as defined in claim 1, wherein light is extracted from the active region through the superstrate.

12. A light-emitting device, as defined in claim 1, further comprising:

a submount;

an n-interconnect connecting the n-electrode to the submount; and

a p-interconnect connecting the p-electrode to the submount.

13. A light-emitting device, as defined in claim 12, wherein the n-interconnect and p-interconnect are selected from the group consisting of solder, elemental metals, metal alloys, semiconductor-metal alloys, thermally and electrically conductive pastes, thermally and electrically conductive compounds, epoxies, eutectic joints, Au stud-bumps, and solder bumps.

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

a p-conductive interface disposed between the p-interconnect and the p-electrode; and

an n-conductive interface disposed between the n-interconnect and the n-electrode.

15. A light-emitting device, as defined in claim 14, wherein the p-conductive interface and the n-conductive interface comprise wettable metals.

16. A light-emitting device, as defined in claim 14, wherein the lateral corss sectional area of the n-conductive interface and the p-conductive interface is at least 15% of an area of the p-electrode.

17. A light-emitting device, as defined in claim 14, further comprising a barrier layer disposed between the p-electrode and the p-conductive interface.

18. A light-emitting device, as defined in claim 17, wherein the barrier layer is selected from the group consisting of Ni, Cr, Cu, and Ti.

19. A light-emitting device, as defined in claim 12, wherein the submount comprises a material selected from the group consisting of Si, AlN, and BeO.

20. A light-emitting device, as defined in claim 12, wherein the submount has a thickness less than 250 μ

m.