GaN based LED with improved light extraction efficiency and method for making the same

• US 7,993,943 B2
• Filed: 01/18/2010
• Issued: 08/09/2011
• Est. Priority Date: 08/14/2006
• Status: Active Grant

• Current Assignee: Seoul Semiconductor Co., Ltd.
• Original Assignee: Bridgelux Incorporated
• Inventors: Lester, Steven D.
• Primary Examiner(s): Nguyen; Ha Tran T
• Assistant Examiner(s): CAMPBELL, SHAUN M
• Application Number:
  US12/688,918
• Publication Number:
  US 20100127276A1
• Time in Patent Office: 568 Days
• Field of Search: 438/22, 257E51018-E51022
• US Class Current: 438/22
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

A light-emitting device and the method for making the same are disclosed. The device includes a substrate, a light-emitting structure and a light scattering layer. The light-emitting structure includes an active layer sandwiched between a p-type GaN layer and an n-type GaN layer, the active layer emitting light of a predetermined wavelength when electrons and holes from the n-type GaN layer and the p-type GaN layer, respectively, combine therein. The light scattering layer includes a GaN crystalline layer characterized by an N-face surface. The N-face surface includes features that scatter light of the predetermined wavelength. The light-emitting structure is between the N-face surface and the substrate.

Claims

1. A device comprising:

a substrate;

a light-emitting structure comprising an active layer sandwiched between a p-type GaN layer and an n-type GaN layer, said active layer emitting light of a predetermined wavelength in said active layer when electrons and holes from said n-type GaN layer and said p-type GaN layer, respectively, combine therein;

a transition layer comprising p-type GaN, said transition layer comprising substantially parallel top surface and bottom surfaces, wherein said bottom surface is a first N-face surface facing said substrate, and wherein said top surface exposes a second N-face; and

a light scattering surface comprising a GaN crystalline layer characterized by a third N-face surface, said third N-face surface including features that scatter light of said predetermined wavelength, wherein said transition layer is between said third N-face surface and said substrate; and

wherein said transition layer is directly adjacent said p-type GaN layer.

2. The device of claim 1 wherein said features have dimensions that are greater than said predetermined wavelength in said scattering layer.

3. The device of claim 1 wherein said n-type GaN layer in said light-emitting structure is between said p-type GaN layer in said light emitting structure and said substrate.

4. The device of claim 1 wherein said light scattering surface comprises a first GaN layer that is doped with Mg to a concentration of 10²⁰ atoms/cm³ or greater.

5. The device of claim 4 wherein said light scattering surface comprises a second GaN layer adjacent to said first GaN layer that is doped with Mg to a concentration less than 10²⁰ atoms/cm³.

6. The device of claim 5 wherein said third N-face surface comprises a surface of said second GaN layer.

7. The device of claim 3 wherein said light scattering surface comprises n-type GaN.

8. The device of claim 3 wherein said light scattering surface comprises p-type GaN.