Light-emitting device and method for manufacturing the same

1. A light-emitting device comprising:

a first cladding layer made of a first-type semiconductor material;

a light-emitting layer disposed on said first cladding layer to emit light when supplied with external electricity;

a second cladding layer disposed on said light-emitting layer oppositely of said first cladding layer, and made of a second-type semiconductor material which has an electrical property opposite to that of said first-type semiconductor material;

an epitaxial structure including an indium-containing oxide, and formed on said second cladding layer oppositely of said light-emitting layer;

a transparent conductive layer made of a material different from that of said epitaxial structure, and disposed to overlay said epitaxial structure; and

an electrode unit for supplying the external electricity, including a first electrode disposed to be electrically connected to said first cladding layer, and a second electrode disposed on said transparent conductive layer to be electrically connected to said second cladding layer through said epitaxial structure and said transparent conductive layer such that the external electricity is permitted to be transmitted to said light-emitting layer through said first and second electrodes;

wherein said indium-containing oxide is In y Ga 1-y O where 0<y<1; and

wherein each of said first and second cladding layers and said light-emitting layer is made of a gallium nitride based material.

2. The light-emitting device of claim 1 , wherein said epitaxial structure is configured to have a plurality of growth islands formed on said second cladding layer.

3. The light-emitting device of claim 1 , wherein said epitaxial structure is configured to have an epitaxial film formed on said second cladding layer.

4. The light-emitting device of claim 3 , wherein said epitaxial structure is configured to further have a plurality of growth islands formed on said epitaxial film oppositely of said second cladding layer.

5. The light-emitting device of claim 2 , wherein said growth islands have a mean width ranging from 30 nm to 300 nm, and a mean height ranging from 10 nm to 20 nm.

6. The light-emitting device of claim 2 , wherein a distance between two adjacent ones of said growth islands is greater than 100 nm.

7. The light-emitting device of claim 1 , wherein said epitaxial structure is of an orthorhombic crystal system.

8. The light-emitting device of claim 7 , wherein each of said first and second cladding layers and said light-emitting layer is of a hexagonal crystal system.

9. The light-emitting device of claim 1 , wherein each of said first and second cladding layers, said light-emitting layer, and said epitaxial structure has a single crystal lattice.

10. The light-emitting device of claim 1 , wherein said material of said transparent conductive layer is selected from transparent metal oxides and transparent metals.

11. The light-emitting device of claim 10 , wherein said transparent metal oxides are selected from the group consisting of indium tin oxide, aluminum zinc oxide, indium zinc oxide, and combinations thereof.

12. The light-emitting device of claim 1 , wherein said transparent conductive layer is of a cubic crystal system.

13. The light-emitting device of claim 1 , wherein said transparent conductive layer is amorphous or polycrystalline.

14. A method for manufacturing a light-emitting device, comprising the steps of:

(a) epitaxially growing a first cladding layer on a substrate, the first cladding layer being made of a first-type semiconductor material;

(b) epitaxially growing a light-emitting layer on the first cladding layer, the light-emitting layer being capable of emitting light when supplied with an external electricity;

(c) epitaxially growing a second cladding layer on the light-emitting layer, the second cladding layer being made of a second-type semiconductor material which has an electrical property opposite to that of the first-type semiconductor material;

(d) epitaxially growing an epitaxial structure on the second cladding layer, the epitaxial structure including an indium-containing oxide which is In y Ga 1-y O where 0<y<1;

(e1) forming a transparent conductive layer such that the transparent conductive layer is disposed to overlay the epitaxial structure, the transparent conductive layer being made of a material different from that of the epitaxial structure; and

(e2) forming a first electrode to be electrically connected to the first cladding layer, and forming a second electrode on the transparent conductive layer so as to be electrically connected to the second cladding layer through the epitaxial structure and the transparent conductive layer, such that the external electricity is permitted to be transmitted to the light-emitting layer through the first and second electrodes;

wherein each of the first and second cladding layers and the light-emitting layer is made of a gallium nitride based material.

15. The method of claim 14 , wherein step (d) includes sub-steps of:

(d1) supplying a stream of nitrogen to entrain a gallium source gas and an indium source gas therein so as to introduce the gallium source gas and the indium source gas into a growth chamber for growing the epitaxial structure; and

(d2) supplying an oxygen component source to the growth chamber.

16. The method of claim 14 , wherein the first cladding layer, the light-emitting layer, and the second cladding layer are of a hexagonal crystal system and are respectively grown in steps (a) to (c), and the epitaxial structure is of an orthorhombic crystal system and is grown in step (d).