GaN based LED with improved light extraction efficiency and method for making the same
View Patent ↗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.
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 10 20 atoms/cm 3 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 10 20 atoms/cm 3 .
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.