Light-emitting device and manufacturing method thereof

1. A light-emitting device comprising:

a substrate;

a barrier layer on the substrate, the barrier layer comprising a first metal multilayer and a second metal multilayer directly on the first metal multilayer;

a metal connecting structure located between the substrate and the barrier layer;

a metal reflective layer on the barrier layer; and

a light-emitting stack electrically coupled to the metal reflective layer, wherein the barrier layer is between the light-emitting stack and the substrate;

wherein the first metal multilayer comprises a first metal layer comprising a first metal element and a second metal layer comprising a second metal element, and the first metal layer is closer to the metal connecting structure than the second metal layer is, and the second metal multilayer comprises a third metal layer comprising a third metal element and a fourth metal layer comprising a fourth metal element, and the third metal layer is closer to the second metal layer than the fourth metal layer is, and the first metal element is different from the second metal element, and the third metal element is different from the fourth metal element.

2. The light-emitting device of claim 1 , wherein the metal connecting structure and the metal reflective layer comprise the same metal element.

3. The light-emitting device of claim 1 , wherein the first metal layer consists of the first metal element and the third metal layer consists of the third metal element.

4. The light-emitting device of claim 1 , wherein a thickness of the first metal layer is different from that of the second metal layer.

5. The light-emitting device of claim 4 , wherein the thickness of the first metal layer is larger than that of the second metal layer.

6. The light-emitting device of claim 1 , wherein the light-emitting stack comprises a surface away from the metal connecting structure, and the surface comprises a first part and a second part having a roughness larger than that of the first part.

7. The light-emitting device of claim 6 , further comprising an electrode located on the first part.

8. The light-emitting device of claim 1 , further comprising a dielectric layer between the barrier layer and the light-emitting stack.

9. The light-emitting device of claim 8 , wherein the dielectric layer comprises a plurality of through holes which penetrate the dielectric layer.

10. The light-emitting device of claim 8 , wherein the dielectric layer comprises silicon oxide (SiO x ), magnesium fluoride (MgF 2 ), or silicon nitride (SiN x ).

11. The light-emitting device of claim 1 , wherein the metal reflective layer comprises a fifth metal element different from the first metal element and the second metal element, or the metal connecting structure comprises a sixth metal element different from the first metal element and the second metal element.

12. The light-emitting device of claim 1 , wherein the metal connecting structure comprises indium, gold or both.

13. The light-emitting device of claim 1 , wherein the metal reflective layer comprises gold.

14. The light-emitting device of claim 1 , wherein the first metal layer comprises the same material as the third metal layer.

15. The light-emitting device of claim 3 , wherein the first metal element is the same as the third metal element.

16. The light-emitting device of claim 1 , wherein the first metal element comprises nickel or platinum.

17. The light-emitting device of claim 1 , wherein the second metal layer comprises the same material as the fourth metal layer.

18. The light-emitting device of claim 1 , wherein the second metal layer consists of the second metal element and the fourth metal layer consists of the fourth metal element.

19. The light-emitting device of claim 18 , wherein the second metal element is the same as the fourth metal element.

20. The light-emitting device of claim 1 , wherein the second metal element and the fourth metal element comprise titanium.