Light emitting device

1. A light emitting device, comprising:

a light-enhancing layered structure of a hexagonal crystal system, said light-enhancing layered structure including a light-enhancing layer having a planar surface that is formed with a plurality of light-enhancing units thereon, each of said light-enhancing units extending in a normal direction relative to said planar surface, being tapered from said planar surface, and having three inclined faces that are adjoined side-by-side and that are respectively parallel to corresponding symmetrical ones of the crystal planes {11 2 k } of the hexagonal crystal system, where k =2 to 5; and

a light emitting layered structure formed on said light-enhancing layered structure;

wherein each of said light-enhancing units is in the form of a recessed wall that defines a recess indented inwardly from said planar surface of said light-enhancing layer, and that has a peripheral wall portion defining said inclined faces;

wherein said light-enhancing layered structure further includes a buffer layer formed on said planar surface of said light-enhancing layer and formed with a plurality of protrusions extending respectively into said recesses of said light-enhancing units; and

wherein each of said protrusions intersects said inclined faces of said recessed wall of the respective one of said light-enhancing units so as to form closed cavities therebetween.

2. The light emitting device of claim 1 , wherein said recessed wall of each of said light-enhancing units has a tip end.

3. The light emitting device of claim 1 , wherein said recessed wall of each of said light-enhancing units further has a base wall portion that is triangular in shape, and that has three edges connected respectively to edges of said inclined faces.

4. The light emitting device of claim 1 , wherein said recess has a depth ranging from 0.3 to 5 μm relative to said planar surface of said light-enhancing layer.

5. The light emitting device of claim 1 , wherein said light-enhancing layer is a sapphire substrate.

6. A light emitting device of comprising:

a light-enhancing layered structure of a hexagonal crystal system, said light-enhancing layered structure including a light-enhancing layer having a planar surface that is formed with a plurality of light-enhancing units thereon, each of said light-enhancing units extending in a normal direction relative to said planar surface, being tapered from said planar surface, and having three inclined faces that are adjoined side-by-side and that are respectively parallel to corresponding symmetrical ones of the crystal planes {11 2 k } of the hexagonal crystal system, where k =2 to 5; and

a light emitting layered structure formed on an opposite surface of said light-enhancing layer opposite to said planar surface of said light-enhancing layer;

wherein each of said light-enhancing units is in the form of a protrusion protruding from said planar surface of said light-enhancing layer and having a peripheral wall defining said inclined and faces; and

wherein said light-enhancing units are exposed from said light-enhancing layer and said light emitting layered structure.

7. The light emitting device of claim 6 , wherein said protrusion of each of said light-enhancing units has a tip end.

8. The light emitting device of claim 6 , wherein said protrusion of each of said light-enhancing units further has a base wall portion that is triangular in shape, and that has three edges connected respectively to edges of said inclined faces.