Light-emitting device

1. A light-emitting device, comprising:

a substrate;

a bonding layer on the substrate;

a light-emitting stack on the bonding layer and having a first-type semiconductor layer, a second-type semiconductor layer, and an active layer between the first-type semiconductor layer and the second-type semiconductor layer;

a reflective structure between the first-type semiconductor layer and the substrate;

a void between the substrate and the light-emitting stack;

a first interface between the substrate and the light-emitting stack; and

a second interface on the void;

wherein the void is enclosed and embedded within the light-emitting device and directly contacts the bonding layer, the reflective structure electrically connects to the first-type semiconductor layer at the first interface, and a critical angle at the first interface for a light emitted from the light-emitting stack is larger than that at the second interface.

2. The light-emitting device of claim 1 , wherein the reflective structure comprises a transparent conductive layer, and the first interface is between the first-type semiconductor layer and the transparent conductive layer.

3. The light-emitting device of claim 1 , further comprising an electrode on the light-emitting stack, wherein the electrode comprises an electrode pad, a first extension electrode connecting to the electrode pad.

4. The light-emitting device of claim 3 , wherein the void is at a position not vertically aligned to the electrode pad.

5. The light-emitting device of claim 3 , wherein the electrode further comprises a third extension electrode extending from the electrode pad and having a portion at a position vertically aligned to the void.

6. The light-emitting device of claim 1 , further comprising an electrode on the light-emitting stack, wherein the electrode comprises an electrode pad, and from a cross section view of the light-emitting device, the first interface at a position vertically aligned to the electrode pad has a first width larger than a second width of the electrode pad.

7. The light-emitting device of claim 1 , wherein the reflective structure electrically connects to the first-type semiconductor layer at the first interface.

8. The light-emitting device of claim 1 , wherein the second interface is between the first-type semiconductor layer and the void.

9. The light-emitting device of claim 1 , wherein the second interface is at a position vertically aligned to the void.

10. The light-emitting device of claim 1 , further comprising an electrode on the light-emitting stack, wherein the electrode comprises an electrode pad and a first extension electrode connecting to the electrode pad, and the second interface is at a position vertically aligned to a portion of the first extension electrode and at a position not vertically aligned to the electrode pad.

11. A light-emitting device, comprising:

a light-emitting stack including a first-type semiconductor layer, a second-type semiconductor layer, and an active layer between the first-type semiconductor layer and the second-type semiconductor layer;

a reflective structure having a first interface and a second interface, wherein a critical angle at the first interface for a light emitted from the light-emitting stack is larger than that at the second interface;

a contact layer between the first-type semiconductor layer and the reflective structure, wherein the contact layer includes metal or alloy and electrically connects to the first-type semiconductor layer; and

an electrode pad on the second-type semiconductor layer;

wherein the reflective structure electrically connects to the first-type semiconductor layer at the first interface, and the first interface has a portion at a position vertically aligned to the electrode pad.

12. The light-emitting device of claim 11 , wherein the reflective structure includes a transparent conducive layer.

13. The light-emitting device of claim 11 , wherein the contact layer directly contacts the first-type semiconductor layer to form an ohmic contact.

14. The light-emitting device of claim 11 , wherein the reflective structure includes a metal layer and the contact layer does not contact the metal layer.

15. The light-emitting device of claim 11 , further comprising an extension electrode extending from the electrode pad, wherein the second interface has a portion at a position vertically aligned to the extension electrode.

16. A light-emitting device, comprising:

a light-emitting stack including a first-type semiconductor layer, a second-type semiconductor layer, and an active layer between the first-type semiconductor layer and the second-type semiconductor layer;

a reflective structure having a first interface and a second interface, wherein a critical angle at the first interface for a light emitted from the light-emitting stack is larger than that at the second interface, and an area of the first interface is larger than an area of the second interface in a top view;

a contact layer between the first-type semiconductor layer and the reflective structure, and electrically connects to the first-type semiconductor layer; and

an electrode pad on the second-type semiconductor layer;

wherein the reflective structure electrically connects to the first-type semiconductor layer at the first interface, and the first interface has a portion at a position vertically aligned to the electrode pad.

17. The light-emitting device of claim 16 , wherein the reflective structure includes a transparent conducive layer.

18. The light-emitting device of claim 16 , further comprising a bonding layer connected to the reflective structure and directly contacts the first-type semiconductor layer.

19. The light-emitting device of claim 16 , wherein the reflective structure includes a metal layer and the contact layer does not contact the metal layer.

20. The light-emitting device of claim 16 , further comprising an extension electrode extending from the electrode pad, wherein the second interface has a portion at a position vertically aligned to the extension electrode.