Light-emitting device

1. A light-emitting device, comprising:

a light-emitting stack comprising a first side, a second side opposite to the first side, and an upper surface between the first side and the second side;

a first electrode pad formed on the upper surface;

a second electrode pad formed on the upper surface, wherein the first electrode pad is closer to the first side than the second electrode pad;

a first extension electrode comprising a first section extended from the first electrode pad toward the second electrode pad, and a second section extended from the first electrode pad toward the first side; and

a second extension electrode comprising a first branch and a second branch respectively extended from the second electrode pad, wherein the first branch comprises a first end adjacent to the first side, and the second branch comprises a second end adjacent to the first side;

wherein the first extension electrode is disposed between the first branch and the second branch, and the second section extends without crossing a first straight line linking the first end and the second end.

2. The light-emitting device of claim 1 , wherein the first electrode pad and the second electrode pad are aligned to each other in accordance with a line perpendicular to the first side and the second side.

3. The light-emitting device of claim 1 , wherein the first section and the second section are in stripe form and formed along a second straight line perpendicular to the first side.

4. The light-emitting device of claim 1 , wherein the first branch and the second branch are curved.

5. The light-emitting device of claim 4 , wherein the first and second ends are closer to the first side than the first electrode pad.

6. The light-emitting device of claim 5 , wherein the second section of the first extension electrode comprises a third end and the first and second ends of the first branch and the second branch are closer to the first side than the third end of the second section.

7. The light-emitting device of claim 1 , wherein the light-emitting stack comprises a third side and a fourth side opposite to the third side, and the first side, the second side, the third side and the fourth side form a rectangle.

8. The light-emitting device of claim 7 , wherein the length of the first side is X, the length of the third side is Y, the length of the first section is a, and the length of the second section is b, and (a/b)=C(Y/X)−L, and C is a value between 1.5 and 2, and L is a value between 1 and 1.05.

9. The light-emitting device of claim 8 , wherein Y>X.

10. The light-emitting device of claim 8 , wherein the light-emitting stack is activated by a forward voltage between 3.05 V and 3.11V.

11. The light-emitting device of claim 1 , wherein the light-emitting stack comprises a first semiconductor layer, an active layer formed on the first semiconductor layer, and a second semiconductor layer formed on the active layer, and the first semiconductor layer comprises a mesa devoid of the active layer and the second semiconductor layer and configured to dispose the first electrode pad and the first extension electrode, and the second electrode pad is disposed on the second semiconductor layer.

12. The light-emitting device of claim 11 , wherein the upper surface comprising the second semiconductor layer is uneven.

13. A light-emitting device, comprising:

a light-emitting stack comprising a first semiconductor layer, an active layer formed on the first semiconductor layer, and a second semiconductor layer formed on the active layer wherein the first semiconductor layer comprises a mesa devoid of the active layer and the second semiconductor layer, and the light-emitting stack comprises a first side, a second side opposite to the first side, and an upper surface between the first side and the second side;

a first electrode pad disposed on the mesa of the first semiconductor layer;

a second electrode pad disposed on the second semiconductor layer, wherein the first electrode pad is closer to the first side than the second electrode pad;

a first extension electrode disposed on the mesa of the first semiconductor layer, electrically connecting the first semiconductor layer, and comprising a first section extended from the first electrode pad toward the second electrode pad, and a second section extended from the first electrode pad toward the first side; and

a second extension electrode disposed on the second semiconductor layer, electrically connecting the second semiconductor layer, and comprising a first branch and a second branch respectively extended from the second electrode pad;

wherein the first section and the second section are formed along a second straight line perpendicular to the first side.

14. The light-emitting device of claim 13 , wherein the first semiconductor layer comprises a n-type semiconductor layer.

15. The light-emitting device of claim 13 , wherein the second semiconductor layer comprises a p-type semiconductor layer.

16. The light-emitting device of claim 13 , wherein the first electrode pad and the second electrode pad are aligned to each other in accordance with a line perpendicular to the first side and the second side.

17. The light-emitting device of claim 13 , wherein the first section and the second section are in stripe form and aligned to each other.

18. The light-emitting device of claim 13 , wherein the first branch and the second branch are curved.

19. The light-emitting device of claim 13 , wherein the light-emitting stack comprises a third side and a fourth side opposite to the third side, and the first side, the second side, the third side and the fourth side form a rectangle.

20. The light-emitting device of claim 13 , wherein the length of the first side is X, the length of the third side is Y, the length of the first section is a, and the length of the second section is b, and (a/b)=C(Y/X)L, and C is a value between 1.5 and 2, and L is a value between 1 and 1.05.