Light-emitting device

1. A light-emitting device configured to emit a radiation and having a lasing threshold current and a saturation current greater than the lasing threshold current, the light-emitting device further comprising:

a substrate;

an epitaxial structure comprising a first DBR stack, a light-emitting stack and a second DBR stack and a contact layer in sequence;

wherein the light-emitting device emits coherent light having a far-field angle of less than 15 degrees at a first forward current between the lasing threshold current and the saturation current of the light-emitting device, and emits incoherent light at a second forward current less than the lasing threshold current.

2. The light-emitting device according to claim 1 , wherein the contact layer having a first width, the second DBR stack has a second width greater than the first width, and wherein the light-emitting device further comprises a conductive layer covering the contact layer.

3. The light-emitting device according to claim 2 , further comprising an electrode on the conductive layer, wherein the electrode has an opening to expose the conductive layer.

4. The light-emitting device according to claim 3 , wherein the opening is directly over the contact layer.

5. The light-emitting device according to claim 3 , wherein the opening has a maximum width, and a ratio of the first width to the maximum width is between 0.1 and 3.

6. The light-emitting device according to claim 2 , wherein the contact layer comprises multiple discrete contact regions.

7. The light-emitting device according to claim 1 , wherein the conductive layer comprises transparent conductive material.

8. The light-emitting device according to claim 1 , wherein a conductivity of a portion of the second DBR stack right under the contact layer is substantially the same as a conductivity of the other portion of the second DBR stack not covered by the contact layer.

9. The light-emitting device according to claim 1 , further comprising a current blocking layer and an electrode, wherein the current blocking layer is between the contact layer and the electrode and comprising a first opening to expose the contact layer.

10. The light-emitting device according to claim 1 , which is devoid of an oxidized layer and an ion implanted layer in the second DBR stack.

11. The light-emitting device according to claim 5 , wherein the ratio of the first width to the maximum width is between 0.5 and 1.1.

12. The light-emitting device according to claim 5 , wherein the ratio of the first width to the maximum width is between 0.6 and 0.8.

13. The light-emitting device according to claim 9 , wherein the first opening has a first maximum width, a part of the electrode is in the first opening and contacts the contact layer, and the electrode comprises a second opening having a second diameter less than the first maximum width to expose the contact layer.

14. The light-emitting device according to claim 2 , wherein a part of the electrode vertically overlaps with the contact layer.

15. The light-emitting device according to claim 3 , further comprising a substrate under the epitaxial structure and having a third width, and the electrode having a fourth width, wherein the third width>the second width>fourth width>first width.

16. The light-emitting device according to claim 9 , wherein the electrode covers less than 50% of a surface area of the current blocking layer.

17. The light-emitting device according to claim 9 , wherein the epitaxial structure further comprises a ridge comprising an exposed mesa wall.

18. The light-emitting device according to claim 17 , wherein the current blocking layer covers along the exposed mesa wall.

19. The light-emitting device according to claim 18 , wherein the electrode covers along the exposed mesa wall and the current blocking layer is between the exposed mesa wall and the electrode.

20. The light-emitting device according to claim 1 , wherein the second DBR stack consists essentially of a Group III-V semiconductor material.