Phosphor-coated light emitting diodes including tapered sidewalls, and fabrication methods therefor

• US 20040056260A1
• Filed: 09/09/2003
• Published: 03/25/2004
• Est. Priority Date: 09/19/2002
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Negley, Gerald H., Slater, David B. Jr.
• Granted Patent: US 6,853,010 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil

Abstract

A light emitting diode includes a substrate having first and second opposing faces and a sidewall between the first and second opposing faces that extends at an oblique angle from the second face towards the first face. A conformal phosphor layer is provided on the oblique sidewall. The oblique sidewall can allow more uniform phosphor coatings than conventional orthogonal sidewalls.

Claims

1. A Light Emitting Diode (LED) comprising:

a substrate having first and second opposing faces and a sidewall therebetween that extends at an oblique angle from the second face towards the first face; and

a conformal layer comprising phosphor on the sidewall that extends at an oblique angle from the second face towards the first face.

2. An LED according to claim 1 wherein the oblique angle is an obtuse angle.

3. An LED according to claim 2 wherein the obtuse angle is about 120°

.

4. An LED according to claim 1 wherein the sidewall extends at an oblique angle from the second face to adjacent the first face.

5. An LED according to claim 1 wherein the sidewall extends at an oblique angle from the second face to the first face.

6. An LED according to claim 1 wherein the sidewall is a planar sidewall.

7. An LED according to claim 1 wherein the substrate is a semiconductor substrate.

8. An LED according to claim 1 further comprising a diode region on the first face.

9. An LED according to claim 8 wherein the substrate comprises silicon carbide and wherein the diode region comprises gallium nitride.

10. An LED according to claim 1 wherein the sidewall also extends orthogonal to the first face from the first face towards the second face.

11. An LED according to claim 8 wherein the substrate and diode region are a total of about 175 μ

m thick.

13. An LED according to claim 1 wherein the conformal layer comprising phosphor is between about 2 μ

m and about 100 μ

m thick.

14. An LED according to claim 1 wherein the conformal layer comprising phosphor extends along the entire sidewall that extends at an oblique angle from the second face towards the first face.

15. An LED according to claim 1 wherein the conformal layer comprising phosphor also extends on the second face.

16. An LED according to claim 1 further comprising a reflective contact on the second face.

17. An LED according to claim 16 wherein the reflective contact extends on the entire second face.

18. An LED according to claim 16 wherein the conformal layer comprising phosphor extends on the reflective contact opposite the second face.

19. An LED according to claim 18 wherein the conformal layer comprising phosphor is thinner on the reflective contact than on the oblique sidewall.

12. An LED according to claim 111 wherein the sidewall extends at an oblique angle of about 120°

from the second face for about 173 μ

m to adjacent the first face.

20. A Light Emitting Diode (LED) comprising:

a substrate having first and second opposing faces and a planar sidewall therebetween including a first portion that extends at an obtuse angle from the second face to adjacent the first face and a second portion that extends orthogonal to the first face from the first face towards the second face;

a diode region on the first face;

a reflective contact on the second face; and

a conformal layer comprising phosphor on the first portion of the sidewall that extends at an oblique angle from the second face towards the first face.

21. An LED according to claim 20 wherein the substrate comprises silicon carbide and wherein the diode region comprises gallium nitride.

22. An LED according to claim 20 wherein the substrate and diode region are a total of about 175 μ

m thick, wherein the first portion of the sidewall extends at an obtuse angle of about 120°

from the second face for about 173 μ

m to adjacent the first face and wherein the conformal layer comprising phosphor is between about 2 μ

m and about 100 μ

m thick.

23. An LED according to claim 20 wherein the conformal layer comprising phosphor extends on the entire first portion of the sidewall.

24. A method of fabricating Light Emitting Diodes (LED) comprising:

conformally coating a sidewall, which extends at an oblique angle from a second face of a substrate towards a first face of the substrate, with a layer comprising phosphor.

25. A method according to claim 24 wherein conformally coating further comprises conformally coating the second face with the layer comprising phosphor.