Lateral semiconductor light emitting diodes having large area contacts

• US 9,397,266 B2
• Filed: 01/20/2014
• Issued: 07/19/2016
• Est. Priority Date: 11/14/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Ibbetson, James, Yao, Zhimin James
• Primary Examiner(s): Luu, Chuong A
• Application Number:
  US14/159,209
• Publication Number:
  US 20140151735A1
• Time in Patent Office: 911 Days
• Field of Search: 257/98, 257/99, 257/95, 257/79, 257/13, 257/82, 257/88, 257/E33.025, 257/E33.058, 257/E33.064, 257/E33.068, 257/E33.074, 257/80, 257/116, 257/117, 257/431, 257/436, 257/451
• US Class Current: 1/1
• 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 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• 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 having first and second opposing faces that include therein an n-type layer and a p-type layer, an anode contact that ohmically contacts the p-type layer and extends on the first face, and a cathode contact that ohmically contacts the n-type layer and also extends on the first face. The anode and cathode contacts extend on the first face to collectively cover substantially all of the first face. A small gap may be provided between the contacts.

Claims

1. A light emitting diode (LED) comprising:

a diode region having first and second opposing faces and including therein an n-type layer and a p-type layer;

at least one dielectric layer on said first face;

a first metal layer on said first face and comprising a portion that passes through said at least one dielectric layer to electrically connect said first metal layer to said p-type layer;

a second metal layer on said first face and comprising a portion that passes through said at least one dielectric layer to electrically connect said second metal layer to said n-type layer, wherein said LED emits light from a side of said LED adjacent to said second face;

a filling layer between said first metal layer and said second metal layer; and

a transparent contact between said first metal layer and said diode region, wherein said transparent contact comprises indium tin oxide (ITO).

2. The LED of claim 1, wherein the diode region has a first index of refraction, the transparent contact has a second index of refraction that is lower than the first index of refraction, and the at least one dielectric layer has a third index of refraction that is lower than the second index of refraction.

3. The LED of claim 1, wherein at least one of said first and second metal layers is reflective.

4. The LED of claim 1, wherein said transparent contact is between said dielectric layer and said diode region.

5. The LED of claim 1, wherein said at least one dielectric layer is transparent.

6. The LED of claim 1, wherein said at least one dielectric layer comprises silicon dioxide (SiO₂).

7. The LED of claim 1, wherein said at least one dielectric layer comprises multiple layers.

8. The LED of claim 1, wherein said at least one dielectric layer comprises a distributed Bragg reflector (DBR).

9. The LED of claim 1, wherein said transparent contact comprises a transparent conductive oxide.

10. The LED of claim 1, wherein said first and second metal layers extend on said first face to collectively cover at least about 85% of said first face.

11. The LED of claim 1, wherein said first and second metal layers extend on said first face to collectively cover at least about 90% of said first face.

12. The LED of claim 1, wherein said first and second metal layers extend on said first face to collectively cover at least about 93% of said first face.

13. The LED of claim 1, further comprising:

a reflective contact electrically connecting said second metal layer to said n-type layer; and

a transparent insulating layer extending on said transparent contact,

wherein said reflective contact also extends on said transparent insulating layer that is on said transparent contact to cover at least a portion of said transparent contact.

14. The LED of claim 1, further comprising a current spreading layer between said first metal layer and said transparent contact.

15. The LED of claim 1, wherein the portion of said first metal layer that passes through said at least one dielectric layer is defined by a via.

16. The LED of claim 1, wherein the portion of said second metal layer that passes through said at least one dielectric layer is defined by a via.

17. The LED of claim 1, wherein said first and second metal layers extend on said first face in closely spaced apart relation to one another to define a gap there between.

18. The LED of claim 17, wherein said filling layer fills the gap.

19. The LED of claim 17, wherein the filling layer comprises polyimide.

20. The LED of claim 17, wherein the filling layer completely fills the gap.

21. The LED of claim 17, wherein the gap is approximately 75 micrometers wide.

22. The LED of claim 1, wherein said at least one dielectric layer has an index of refraction of approximately 2 or less.

23. The LED of claim 1, wherein said at least one dielectric layer has an index of refraction of approximately 1.5 or less.

24. A light emitting diode (LED) comprising:

a diode region having first and second opposing faces and including therein an n-type layer and a p-type layer;

an anode pad that electrically contacts said p-type layer and extends on the first face;

a cathode pad that electrically contacts the n-type layer and also extends on the first face, such that a gap is defined that extends along the first face between the anode and cathode pads, wherein the anode and cathode pads are adjacent to each other and extend to said gap therebetween; and

a filling layer in the gap.

25. The LED of claim 24, wherein the filling layer comprises polyimide.

26. The LED of claim 24, wherein the filling layer completely fills the gap.

27. The LED of claim 24, wherein the gap is approximately 75 micrometers wide.

28. A light emitting diode (LED) comprising:

an n-type semiconductor layer;

a p-type semiconductor layer;

an anode contact electrically contacting said p-type layer;

a cathode contact electrically contacting said n-type layer and electrically isolated from said anode;

wherein said cathode contact overlaps said anode contact and contacts said n-type layer.

29. The LED of claim 28, further comprising a growth substrate on said n-type layer opposite said p-type layer.

30. The LED of claim 28, wherein said cathode contact comprises at least one via portion that extends through said p-type layer to electrically connect to said n-type layer.

31. The LED of claim 30, wherein said at least one via portion is surrounded by a sidewall of said p-type layer and electrically isolated therefrom by said insulating layer.

32. The LED of claim 30, wherein said at least one via portion is at least partially surrounded by a sidewall of said p-type layer and electrically isolated therefrom by said insulating layer.

33. The LED of claim 28, wherein said cathode contact comprises a plurality of distinct via portions that extend through said p-type layer to electrically connect to said n-type layer.

34. The LED of claim 28, further comprising an insulating layer that electrically isolates said anode contact and said cathode contact.

35. The LED of claim 34, wherein said insulating layer is optically transparent.

36. The LED of claim 34, said insulating layer having an index of refraction of approximately 2 or less.

37. The LED of claim 34, said insulating layer having an index of refraction of approximately 1.5 or less.

38. The LED of claim 28, wherein said cathode contact contacts said n-type layer on multiple sides of said anode contact.