Light emitting diode and fabrication method thereof

1. A light-emitting diode (LED), comprising:

a light-emitting epitaxial layer having a first surface as a light-emitting surface and a second, opposing, surface, including a first type semiconductor layer, an active layer, and a second type semiconductor layer;

a metal reflective layer disposed over the second surface; and

a protective layer formed seamlessly on a surface of the metal reflective layer and on a side wall of the metal reflective layer;

the LED further comprising, between the second surface and the metal reflective layer;

a transparent dielectric layer disposed over the second surface and having conductive through-holes therein;

a first transparent adhesive layer disposed on a surface of the transparent dielectric layer that is distal from the light-emitting epitaxial layer, and covering the conductive through-holes; and

a second transparent adhesive layer disposed on a surface of the first transparent adhesive layer that is distal from the transparent dielectric layer.

2. The LED of claim 1 , wherein an angle between the side wall of the metal reflective layer and the second surface is 30°-85°.

3. The LED of claim 1 , wherein a thickness of the transparent dielectric layer is more than 50 nm.

4. The LED of claim 1 , wherein the is first transparent adhesive layer a transparent insulative adhesive layer covering the surface of the transparent dielectric layer that is distal from the light-emitting epitaxial layer.

5. The LED of claim 1 , wherein the first transparent adhesive layer has a thickness less than 20 nm.

6. The LED of claim 1 , wherein the second transparent adhesive layer is a transparent conductive adhesive layer.

7. The LED of claim 6 , further comprising, between the second surface and the metal reflective layer:

a transparent dielectric layer disposed over the second surface and having conductive through-holes therein, and comprising at least a first layer proximal to the light-emitting epitaxial layer, and a second layer distal from the light-emitting epitaxial layer;

the second layer has a thin-layer structure with a thickness less than 1/10 of a thickness of the first layer, and is configured as an adhesive layer of the first layer.

8. The LED of claim 7 , wherein the first layer comprises multiple sub-layers, and the thickness of the second layer is less than ⅕ of a thickness of any of the multiple sub-layers of the first layer.

9. The LED of claim 7 , wherein the thickness of the first layer of the transparent dielectric layer is more than 50 nm.

10. The LED of claim 7 , wherein the thickness of the second layer of the transparent dielectric layer is less than 20 nm.

11. The LED of claim 7 , wherein the transparent conductive adhesive layer has a thickness less than 10 nm.

12. The LED of claim 7 , wherein:

the first layer of the transparent dielectric layer is an MgF layer;

the second layer of the transparent dielectric layer is a silicon oxide layer;

the transparent conductive adhesive layer is an ITO layer; and

the metal reflective layer is a silver reflector.

13. The LED of claim 1 , wherein a thickness of the second transparent adhesive layer is less than 10 nm.

14. The LED of claim 1 , wherein a thickness of the first transparent adhesive layer is less than 1/10 of the thickness of the transparent dielectric layer.

15. The LED of claim 1 , wherein:

the transparent dielectric layer comprises a plurality of sub-layers; and

a thickness of the first transparent adhesive layer is less than ⅕ of a thickness of any sub-layer of the transparent dielectric layer.

16. The LED of claim 1 , wherein:

the transparent dielectric layer is an MgF layer;

the first transparent adhesive layer is a silicon oxide layer;

the second transparent adhesive layer is an ITO layer; and

the metal reflective layer is a silver reflector.

17. The LED of claim 1 , wherein:

the conductive holes are filled with a metal ohmic contact layer;

a surface of the metal ohmic contact layer at a side that is distal from the epitaxial layer is flush with the first transparent adhesive layer.

18. A light emitting diode (LED) manufacturing method, comprising:

providing a light-emitting epitaxial layer having a first surface as a light-emitting surface and a second, opposing, surface, including a first type semiconductor layer, an active layer, and a second type semiconductor layer;

forming a metal reflective layer over the second surface;

wet etching a peripheral region of the metal reflective layer to form a regular trapezoid or rectangular cross section; and

forming a protective layer seamlessly covering an upper surface of the metal reflective layer and a side wall of the metal reflective layer;

wherein said wet etching comprises:

pre-processing peripheral region of the metal reflective layer;

forming a mask layer on the metal reflective layer exposing at least the pre-processed peripheral region of the metal reflective layer; and

etching the metal reflective layer, wherein the pre-processed peripheral region has a higher etching rate, and the etched metal reflective layer has a regular trapezoid or rectangular cross section.

19. The method of claim 18 , wherein the pre-processing comprises oxidizing.

20. The method of claim 19 , wherein the pre-processing comprises forming an isolation layer at a central region of the metal reflective layer for protection, and then perform the oxidizing of the peripheral region of the metal reflective layer.

21. The method of claim 18 , wherein the forming the metal reflective layer comprises:

forming a transparent dielectric layer over the second surface and having conductive through-holes therein;

forming a first transparent adhesive layer on an upper surface of the transparent dielectric layer, and covering side walls of the conductive through-holes and the upper surface of the transparent dielectric layer;

forming a second transparent adhesive layer over the transparent dielectric layer; and

forming the metal reflective layer over the second transparent adhesive layer.

22. The method of claim 18 , wherein the forming the metal reflective layer comprises:

forming a transparent dielectric layer over the second surface and having conductive through-holes therein, and comprising at least a first layer proximal to the light-emitting epitaxial layer, and a second layer distal from the light-emitting epitaxial layer; wherein the second layer has a thin-layer structure with a thickness less than 1/10 of a thickness of the first layer, and is configured as an adhesive layer of the first layer;

forming a transparent adhesive layer on the transparent dielectric layer; and

forming the metal reflective layer over the transparent adhesive layer.