Led packages having improved light extraction

• US 20040070004A1
• Filed: 11/20/2003
• Published: 04/15/2004
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: Gelcore (General Electric Company)
• Original Assignee: Gelcore (General Electric Company)
• Inventors: Karlicek, Robert F. Jr., Eliashevich, Ivan, Venugopalan, Hari
• Granted Patent: US 7,015,516 B2
• Time in Patent Office: Days
• US Class Current: 257/200
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

A light-emitting microelectronic package includes a light-emitting diode (110) having a first region (114) of a first conductivity type, a second region (116) of a second conductivity type, and a light-emitting p-n junction (118) between the first and second regions. The light-emitting diode defines a lower contact surface (120) and a mesa (122) projecting upwardly from the lower contact surface. The first region (114) of a first conductivity type is disposed in the mesa (122) and defines a top surface of the mesa, and the second region (116) of a second conductivity type defines the lower contact surface that substantially surrounds the mesa (122). The mesa includes at least one sidewall (130) extending between the top surface (124) of the mesa and the lower contact surface (120), the at least one sidewall (130) having a roughened surface for optimizing light extraction from the package.

Claims

1. A light-emitting microelectronic package comprising:

a light-emitting diode including a first region of a first conductivity type, a second region of a second conductivity type, and a light-emitting p-n junction between said first and second regions, said light-emitting diode defining a lower contact surface and a mesa projecting upwardly from said lower contact surface, said first region of a first conductivity type being disposed in said mesa and defining a top surface of said mesa, said second region of a second conductivity type defining said lower contact surface that substantially surrounds said mesa, wherein said mesa includes at least one sidewall extending between said top surface of said mesa and said lower contact surface, said at least one sidewall having a roughened surface for improving light extraction from said package.

2. The package as claimed in claim 1, wherein said light-emitting diode is a GaN semiconductor.

3. The package as claimed in claim 1, wherein said light-emitting diode overlies a substantially transparent dielectric substrate .

4. The package as claimed in claim 3, wherein said substantially transparent dielectric substrate has a top surface, a bottom surface and at least one sidewall extending between said top and bottom surfaces.

5. The package as claimed in claim 4, wherein said at least one sidewall of said substantially transparent dielectric substrate has a roughened surface.

6. The package as claimed in claim 3, wherein said package has a width and a height, the ratio of said width to said height defining an aspect ratio for said package that is 2:

1 or less.

7. The package as claimed in claim 1 wherein said light-emitting diode further comprises:

an upper contact accessible at the top surface of said mesa; and

a lower contact accessible at the lower contact surface of said diode.

8. The package as claimed in claim 1, wherein said mesa is generally in the form of a rectangular solid and said top surface of said mesa is substantially rectangular.

9. The package as claimed in claim 8, wherein the top surface of said mesa is substantially square.

10. The package as claimed in claim 1 wherein said lower contact is a substantially rectangular loop overlying said lower contact surface and substantially surrounding said mesa.

11. The package as claimed in claim 1, wherein said light-emitting diode includes an indentation in at least one sidewall of said mesa, said indentation extending downwardly from the top surface of said mesa to said lower contact surface, said lower contact being at least partially disposed within said indentation.

12. The package as claimed in claim 11, wherein said indentation extends into said mesa at a corner of the top surface of said mesa.

13. The package as claimed in claim 1, wherein said first conductivity type is a p-type and said second conductivity type is an n-type.

14. The package as claimed in claim 1, wherein said substantially transparent substrate comprises a material selected from the group consisting of sapphire, GaN, AIN, ZnO, and LiGaO.

15. The package as claimed in claim 1, wherein said light-emitting diode is a GaN light-emitting diode and said substantially transparent dielectric substrate is made of sapphire.

16. A light-emitting diode package comprising:

a substantially transparent dielectric substrate having a top surface, a bottom surface and at least one sidewall extending between the top and bottom surfaces;

a light-emitting diode overlying said substantially transparent dielectric substrate, said light-emitting diode including a first region of a first conductivity type, a second region of a second conductivity type and a light-emitting p-n junction between said regions, wherein the at least one sidewall of said substantially transparent dielectric substrate has a roughened surface.

17. The package as claimed in claim 16, wherein said light-emitting diode defines a lower contact surface and a mesa projecting upwardly from said lower contact surface, said first region of a first conductivity type being disposed in said mesa and defining a top surface of said mesa, said second region of a second conductivity type defining said lower contact surface that substantially surrounds said mesa, wherein said mesa includes at least one sidewall extending between said top surface of said mesa and said lower contact surface.

18. The package as claimed in claim 17, wherein said at least one sidewall of said mesa has a roughened surface for improving light extraction from said package.

19. The package as claimed in claim 17, wherein said light-emitting diode is a GaN semiconductor.

20. A light-emitting microelectronic package comprising:

a substantially transparent dielectric substrate having a top surface, a bottom surface and at least one sidewall extending between the top and bottom surfaces;

a light-emitting diode overlying said substantially transparent dielectric substrate, said light-emitting diode including a first region of a first conductivity type, a second region of a second conductivity type and a light-emitting p-n junction between said regions that emits light having a wavelength, wherein the at least one sidewall of said substantially transparent dielectric substrate includes a roughened surface having a pattern that is matched to the wavelength of the light emitting by the light-emitting p-n junction for optimizing the amount of light emitted from said package.

21. The package as claimed in claim 20, wherein said light-emitting diode is a GaN semiconductor and said substrate is made of sapphire.

22. A method of making a light-emitting microelectronic package comprising:

providing a substantially transparent dielectric substrate having a top surface and a bottom surface;

securing one or more light-emitting diodes over the top surface of said substantially transparent dielectric substrate;

after securing the one or more light-emitting diodes, separating said substantially transparent dielectric substrate to provide individual light-emitting packages having a height, each said individual package including at least one of the light-emitting diodes secured over a separated portion of said substantially transparent dielectric substrate, wherein each of the separated portions of said substrate has a width, the width of said substrate being no greater than twice a height of said package.

23. The method as claimed in claim 22, wherein each said separated substrate portion has at least one sidewall extending between the top and bottom surfaces thereof, the method further comprising roughening said at least one sidewall of said substrate.

24. The method as claimed in claim 23, wherein the roughening step includes etching said at least one sidewall.

25. The method as claimed in 21, wherein the roughening step includes separating said substrate using a saw or using laser ablation.

26. A method of making a light-emitting microelectronic package comprising:

forming a light-emitting diode including a first region of a first conductivity type, a second region of a second conductivity type, and a light-emitting p-n junction between said first and second regions, said light-emitting diode defining a lower contact surface and a mesa projecting upwardly from said lower contact surface, said first region of a first conductivity type being disposed in said mesa and defining a top surface of said mesa, said second region of a second conductivity type defining said lower contact surface, said lower contact surface substantially surrounding said mesa, wherein said mesa includes at least one sidewall extending between the top surface of said mesa and the lower contact region;

roughening said at least one sidewall of said mesa for improving light extraction from said package.

27. The method as claimed in claim 26, mounting said light-emitting diode atop a substantially transparent dielectric substrate, wherein light generated by said light-emitting diode is passable through said dielectric substrate.

28. The method as claimed in claim 27, wherein said substantially transparent dielectric substrate has one or more sidewalls, the method further comprising roughening at least one of said one or more sidewalls.