Highly reflective ohmic contacts to III-nitride flip-chip LEDs

• US 6,573,537 B1
• Filed: 03/29/2001
• Issued: 06/03/2003
• Est. Priority Date: 12/22/1999
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Wierer, Jonathan J. Jr., Lester, Steven D., Steigerwald, Daniel A.
• Primary Examiner(s): Flynn, Nathan J.
• Assistant Examiner(s): Forde, Remmon R.
• Application Number:
  US09/821,684
• Time in Patent Office: 796 Days
• Field of Search: 257/103, 257/94-96, 257/98, 257/99, 257/79, 257/91, 257/11-13, 257/436, 257/741
• US Class Current: 257/103
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/0558 being stacked
• CPC Class Codes: H01L 2224/05611 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05639 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05666 Titanium [Ti] as principal constituent
• CPC Class Codes: H01L 2224/05669 Platinum [Pt] as principal constituent
• CPC Class Codes: H01L 2224/05671 Chromium [Cr] as principal constituent
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• 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 25/0753 the devices being arranged next to each other
• 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 2924/00014 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/08 : with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/32 : containing nitrogen
• CPC Class Codes: H01L 33/38 : with a particular shape
• CPC Class Codes: H01L 33/405 : Reflective materials
• CPC Class Codes: H01L 33/60 : Reflective elements
• 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

An inverted III-nitride light-emitting device (LED) with highly reflective ohmic contacts includes n- and p-electrode metallizations that are opaque, highly reflective, and provide excellent current spreading. The n- and p-electrodes each absorb less than 25% of incident light per pass at the peak emission wavelength of the LED active region.

Claims

1. A light-emitting device comprising:

a III-nitride device comprising an n-type layer, a p-type layer, and an emission layer, interposing the n-type and p-type layers, being operative to emit light λ

; and

an n-electrode connected to the n-type layer and a p-electrode connected to the p-type layer, wherein both the n-electrode and the p-electrode are formed on a same side of the device and the n-electrode has a normal incidence reflectivity exceeding 80% for light emitted by the emission layer.

2. A light-emitting device, as defined in claim 1, wherein the p-electrode has an absorption less than 10%.

3. A light-emitting device, as defined in claim 1, wherein the n-electrode has an absorption less than 20%.

4. A light-emitting device, as defined in claim 1, wherein each electrode comprises silver.

5. A light-emitting device, as defined in claim 1, wherein each electrode comprises aluminum.

6. A light-emitting device, as defined in claim 1, wherein the p-electrode comprises silver.

7. A light-emitting device, as defined in claim 1, wherein the p-electrode comprises aluminum.

8. A light-emitting device, as defined in claim 1, wherein the n-electrode comprises silver.

9. A light-emitting device, as defined in claim 1, wherein the n-electrode comprises aluminum.

10. A light-emitting device, as defined in claim 1, further comprising a substrate wherein the n-type and p-type layers are sandwiched between the substrate and the n- and p-electrodes, and

wherein light escapes the device through the substrate.

11. A light-emitting device, as defined in claim 10, wherein the substrate comprises sapphire.

12. A light-emitting device, as defined in claim 10, wherein the substrate comprises silicon carbide.

13. A light-emitting device, as defined in claim 10, wherein the substrate comprises gallium nitride.

14. A light-emitting device, as defined in claim 1, wherein the n-electrode further comprises a first portion and a second portion, wherein the p-electrode interposes the first and second portion.

15. A light-emitting device, as defined in claim 14, wherein the first and second portions are substantially parallel, the n-electrode further comprising a third portion substantially perpendicular to the first and second portions and connecting the first and section portions.

16. A light-emitting device, as defined in claim 1, wherein the p-electrode further comprises a first portion and a second portion, wherein the n-electrode interposes the first and second portion.

17. A light-emitting device, as defined in claim 1, wherein an area of the p-electrode is at least five times an area of the n-electrode.

18. A light-emitting device, as defined in claim 1, wherein the p-electrode comprises at least 50% of a surface area of the device.

19. A light-emitting device, as defined in claim 1, wherein the n-electrode comprises about 10% to about 15% of a surface area of the device.