Light emitting diodes including optically matched substrates

• US 8,692,277 B2
• Filed: 07/13/2010
• Issued: 04/08/2014
• Est. Priority Date: 02/01/2001
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Slater, David B. Jr., Glass, Robert C., Swoboda, Charles M., Keller, Bernd, Ibbetson, James, Thibeault, Brian, Tarsa, Eric J.
• Primary Examiner(s): Jackson, Jr., Jerome
• Application Number:
  US12/835,366
• Publication Number:
  US 20100283077A1
• Time in Patent Office: 1,365 Days
• Field of Search: 257/95, 257/99
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/32014 the layer connector being smaller than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• 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

Abstract

Light emitting diodes include a diode region comprising a gallium nitride-based n-type layer, an active region and a gallium nitride-based p-type layer. A substrate is provided on the gallium nitride-based n-type layer and optically matched to the diode region. The substrate has a first face remote from the gallium nitride-based n-type layer, a second face adjacent the gallium nitride-based n-type layer and a sidewall therebetween. At least a portion of the sidewall is beveled, so as to extend oblique to the first and second faces. A reflector may be provided on the gallium nitride-based p-type layer opposite the substrate. Moreover, the diode region may be wider than the second face of the substrate and may include a mesa remote from the first face that is narrower than the first face and the second face.

Claims

1. A light emitting diode comprising:

a diode region comprising a gallium nitride-based n-type layer, an active region and a gallium nitride-based p-type layer;

a substrate on the gallium nitride-based n-type layer and optically matched to the diode region, the substrate having a first face remote from the gallium nitride-based n-type layer, a second face adjacent the gallium nitride-based n-type layer and a sidewall therebetween, at least a portion of the sidewall being beveled so as to extend oblique to the first and second faces;

a reflector on the gallium nitride-based p-type layer remote from the substrate;

a first bonding layer on the reflector remote from the substrate;

an ohmic contact on the gallium nitride-based n-type layer remote from the substrate; and

a second bonding layer on the ohmic contact remote from the substrate,

wherein the first face further comprises two intersecting grooves therein that form an X-shape in plan view.

2. A light emitting diode according to claim 1 wherein the ohmic contact comprises reflective material.

3. A light emitting diode according to claim 1 wherein the substrate is directly on the gallium nitride-based n-type layer to define an interface therebetween, wherein the interface is planar.

4. A light emitting diode according to claim 1 wherein the first face of the substrate is textured.

5. A light emitting diode according to claim 1 wherein the substrate comprises silicon carbide.

6. A light emitting diode according to claim 1 further comprising a first barrier layer between the reflector and the first bonding layer and a second barrier layer between the ohmic contact and the second bonding layer.

7. A light emitting diode according to claim 1 wherein the gallium nitride-based n-type layer includes a thick portion that is on the active region and a thin portion that is offset from the active region and wherein the ohmic contact is on the thin portion, remote from the substrate.

8. A light emitting diode according to claim 1 wherein the first and second bonding layers are coplanar.

9. A light emitting diode according to claim 8:

wherein the ohmic contact comprises reflective material;

wherein the substrate is directly on the gallium nitride-based n-type layer to define an interface therebetween, wherein the interface is planar; and

wherein the substrate comprises silicon carbide.

10. A light emitting diode according to claim 9 further comprising a first barrier layer between the reflector and the first bonding layer and a second barrier layer between the ohmic contact and the second bonding layer.

11. A light emitting diode according to claim 9 wherein the gallium nitride-based n-type layer includes a thick portion that is on the active region and a thin portion that is offset from the active region and wherein the ohmic contact is on the thin portion, remote from the substrate.

12. A light emitting diode comprising:

a substrate having a first face and a second face that is wider than the first face; and

a semiconductor diode region on the second face, remote from the first face, that is optically matched to the substrate and that is wider than the second face, so that a portion of the semiconductor diode region overhangs beyond a widest portion of the second face,

wherein the substrate includes at least one groove in the first face and a beveled sidewall between the first and second faces.

13. A light emitting diode according to claim 12 wherein the diode region includes a first portion adjacent the second face that is wider than the second planar face and a second portion remote from the second face that is narrower than the first portion to define a mesa.

14. A light emitting diode according to claim 13 wherein the second portion is also narrower than the second face.

15. A light emitting diode according to claim 14 further comprising a contact on the mesa remote from the first portion that is narrower than the mesa.

16. A light emitting diode according to claim 14 wherein the second portion is also at least as narrow as the first face.

17. A light emitting diode according to claim 12:

wherein the substrate is on the diode region and has a sidewall between the first face and the second face, at least a portion of the sidewall being beveled so as to extend oblique to the first and second faces.

18. A light emitting diode according to claim 17 wherein the substrate is directly on the diode region to define an interface therebetween, wherein the interface is planar.

19. A light emitting diode according to claim 12 wherein the substrate comprises silicon carbide.

20. A light emitting diode according to claim 13:

wherein the diode region comprises an active region; and

wherein the active region is confined to the mesa.

29. A light emitting diode according to claim 12 wherein the at least one groove comprises two intersecting grooves that form an X-shape in plan view.

21. A light emitting diode comprising:

a diode region comprising an n-type layer, an active region and a p-type layer;

an anode contact on the p-type layer; and

a cathode contact on the n-type layer,

wherein the anode contact and the cathode contact are coplanar and the cathode contact is thicker than the anode contact; and

a substrate having an inner face on the n-type layer remote from the coplanar anode and cathode contacts, an outer face and a beveled sidewall between the inner face and the outer face,

wherein the substrate includes at least one groove in the outer face.

22. A light emitting diode according to claim 21 wherein the coplanar anode and cathode contacts are configured for flip-chip mounting of the light emitting diode.

23. A light emitting diode according to claim 21 in combination with a mounting support, wherein the coplanar anode and cathode contacts are mounted on the mounting support.

24. A light emitting diode according to claim 23 wherein the coplanar anode and cathode contacts are mounted directly on the mounting support.

25. A light emitting diode according to claim 23 in further combination with a dome that extends from the mounting support to surround the light emitting diode.

30. A light emitting diode according to claim 21 wherein the at least one groove comprises two intersecting grooves that form an X-shape in plan view.

26. A light emitting diode comprising:

a substrate having a first face and a second face that is wider than the first face;

a semiconductor diode region on the second face, remote from the first face, that is optically matched to the substrate; and

a pair of electrical contacts for the diode region that are both on the diode region remote from the substrate;

wherein the substrate includes at least two intersecting grooves in the first face that form an X-shape in plan view, and a beveled sidewall between the first and second faces.

27. A light emitting diode according to claim 26 wherein the pair of electrical contacts have coplanar outer surfaces.

28. A light emitting diode according to claim 26 wherein the pair of electrical contacts comprise reflective electrical contacts.