Electrode structures for light emitting devices

• US 6,307,218 B1
• Filed: 11/20/1998
• Issued: 10/23/2001
• Est. Priority Date: 11/20/1998
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.), Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Rudaz, Serge L, Fletcher, Robert M., Thomas, Kyle J., Lester, Steven D., Martin, Paul S., Kish, Fred A. Jr., Imler, William R., Steigerwald, Daniel A., Maranowski, Steven A.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): Wille, Douglas A.
• Application Number:
  US09/196,928
• Time in Patent Office: 1,068 Days
• Field of Search: 257/99, 257/91, 257/94, 257/96
• US Class Current: 257/99
• 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

Abstract

A light emitting device includes a heterojunction having a p-type layer and an n-type layer. The n-electrode is electrically connected to the n-type layer while the p-electrode is electrically connected to the p-type layer. The p and n-electrodes are positioned to form a region having uniform light intensity.

Claims

1. A light emitting device comprising:

a device structure of an AlInGaN material system, the device having a top surface, the top surface comprising a light emitting region covering at least 60% of a total area of the top surface;

a heterojunction within the device structure, the heterojunction comprising a p-type and an n-type semiconductor layer; and

a p-electrode and an n-electrode positioned on the top surface, the p-electrode being electrically connected to the p-type semiconductor layer, the n-electrode being electrically connected to the n-type semiconductor layer, one of the p-electrode and the n-electrode having a varying width.

2. A light emitting device, as defined in claim 1, wherein a length of one of the p-electrode and the n-electrode is ≧

65% of a length of one side of the top surface.

3. A light emitting device, as defined in claim 1, wherein:

the top surface of the device structure is a polygon; and

a length of one of the p-electrode and the n-electrode is ≧

65% of a length of each of at least two sides of the polygon.

4. A light emitting device, as defined in claim 3, wherein the inner contours of the p-electrode and the n-electrode are parallel to the sides of the polygon.

5. A light emitting device, as defined in claim 3, wherein the inner contours of the p-electrode and the n-electrode are parallel to each other.

6. A light emitting device, as defined in claim 3, wherein the polygon is selected from a group consisting of squares, hexagons, octagons, rectangles, trapezoids, and parallelograms.

7. A light emitting device, as defined in claim 3, each of the p-electrode and the n-electrode further comprising:

a wire bonding area, positioned at a first end of the electrode; and

a second end of the electrode opposite the first end, wherein the second end is narrower than the first end.

8. A light emitting device, as defined in claim 1, wherein:

a shape of the top surface is selected from a group consisting of circles, ellipses, and ovals; and

at least one of the p-electrode and the n-electrode has a length that is ≧

25% of a peripheral length of the top surface.

9. A light emitting device, as defined in claim 1, wherein:

one of the p-electrode and the n-electrode is an enclosing electrode having a shape that encloses 100% of the light emitting region.

10. A light emitting device, as defined in claim 9, wherein the shape of an outside edge of the enclosing electrode is selected from a group consisting of rectangles, circles, squares, parallelograms, ellipses, and ovals.

11. A light emitting device, as defined in claim 9, wherein the shape of an inside edge of the enclosing electrode includes projections operative to spread current in a corresponding semiconductor layer.

12. A light emitting device, as defined in claim 1, further comprising multiple n and p electrodes, positioned to define Q electrically connected regions, Q≧

2, and enclose the light emitting area.

13. A light emitting device, as defined in claim 12, wherein the Q electrically connected regions are connected using multilevel metallization.

19. A light emitting device, as defined in claim 1,

wherein the area of the device structure is ≧

0.2mm².

20. A light emitting device, as defined in claim 9,

wherein the area of the device structure is >

0.2mm².

26. The light emitting device of claim 9 wherein the other of the p-electrode and the n-electrode is within an enclosure formed by the enclosing electrode.

14. A light emitting device comprising:

a device structure of an AlInGaN material system, the device structure having a top surface;

a heterojunction within the device structure the heterojunction comprising a p-type and an n-type semiconductor layer; and

a p-electrode and an n-electrode positioned on the top surface, the p-electrode being electrically connected to the p-type semiconductor layer and the n-electrode being electrically connected to the n-type semiconductor layer;

one of the p-electrode and the n-electrode comprising two outer arms and N inner arms, where N≧

0, and a cross beam connecting the two outer and N inner arms.

15. A light emitting device, as defined in claim 14, further comprising connection pads interposing the two outer and N inner arms.

16. A light emitting device, as defined in claim 15, wherein the other of the p-electrode and the n-electrode is shaped as a fork having M tines, where M≧

1.

17. A light-emitting device, as defined in claim 16, wherein the M tines interpose the two outer and N inner arms.

18. A light emitting device, as defined in claim 17, wherein the distance between the N inner arms and the M tines is constant.

21. A light emitting device, as defined claim 14, further comprising:

an area utilization ratio, of at least 60%, defined as the ratio of the area of the light emitting region to the total area of the device structure; and

wherein the area of the device structure is ≧

0.2 mm².

22. A light emitting device, as defined in claim 21, further comprising connection pads interposing the two outer and N inner arms.

23. A light emitting device, as defined in claim 21, wherein the other of the p and n electrodes is shaped as a fork having M tines, where M≧

1.

24. A light-emitting device, as defined in claim 23, wherein the M tines interpose the two outer and N inner arms.

25. A light emitting device, as defined in claim 24, wherein the distance between the N inner arms and the M tines is constant.

27. The light emitting device of claim 14 wherein a length of at least one of the outer arms is substantially equal to a length of an edge of the heterojunction.

28. A light emitting device, comprising:

a device structure of an AlInGaN material system, the device structure having a top surface;

a heterojunction within the device structure, the heterojunction comprising a p-type and an n-type semiconductor layer; and

a p-electrode and an n-electrode positioned on the top surface, the p-electrode being electrically connected to the p-type semiconductor layer and the n-electrode being electrically connected to the n-type semiconductor layer, the p-electrode further comprising an outer edge located proximate a first boundary of the top surface and a curved edge opposite the outer edge of the p-electrode, and the n-electrode further comprising an outer edge located proximate a second boundary of the top surface and a curved edge opposite the outer edge of the n-electrode;

wherein the first boundary and the second boundary are substantially parallel.

29. The light emitting device of claim 28 wherein a shortest distance between any point on the curved edge of the p-electrode and the n-electrode is constant.

30. The light emitting device of claim 29 wherein said shortest distance is less than a length of at least one edge of the p-electrode.

31. The light emitting device of claim 28 wherein a shape and an area of the p-electrode and the n-electrode are substantially equal.

32. The light emitting device of claim 28 wherein the n-electrode and the p-electrode have a length substantially equal to a length of the heterojunction.

33. A light emitting device comprising:

a device structure of an AlInGaN material system, the device structure having a top surface;

a heterojunction within the device structure, the heterojunction comprising a p-type and an n-type semiconductor layer; and

a p-electrode and an n-electrode positioned on the top surface, the p-electrode being electrically connected to the p-type semiconductor layer and the n-electrode being electrically connected to the n-type semiconductor layer;

wherein one of the p-electrode and the n-electrode comprises two outer arms and a crossbeam connecting the two outer arms and the other of the p-electrode and the n-electrode is located between the two outer arms.

34. The light emitting device of claim 33 wherein the crossbeam has a curved edge.

35. The light emitting device of claim 33 wherein the other of the p-electrode and the n-electrode shaped like a circle.

36. The light emitting device of claim 33 wherein one of the outer arms has a length substantially equal to a length of the heterojunction.