Light-emitting device and manufacturing method thereof
A light-emitting device includes: a substrate having a top surface, wherein the top surface comprises a first portion and a second portion; a first semiconductor stack on the first portion, comprising a first upper surface and a first side wall; and a second semiconductor stack on the first upper surface, comprising a second upper surface and a second side wall, and wherein the second side wall connects the first upper surface; wherein the first semiconductor stack comprises a dislocation stop layer; wherein the dislocation stop layer comprises AlGaN; and wherein the first side wall and the second portion of the top surface form an acute angle α between thereof.
1. A light-emitting device, comprising:
a substrate having a top surface, wherein the top surface comprises a first portion and a second portion;
a first semiconductor stack on the first portion, comprising a first upper surface and a first side wall; and
a second semiconductor stack on the first semiconductor stack, comprising a second upper surface and a second side wall, and wherein the second side wall connects the first upper surface,
wherein the first semiconductor stack comprises a first doped layer and a dislocation stop layer formed between the first portion of the top surface and the first doped layer; wherein the dislocation stop layer comprises AlGaN;
wherein a portion of the first upper surface and a portion of the dislocation stop layer are not covered by the second semiconductor stack,
wherein the first side wall and the second portion of the top surface form an acute angle α between thereof, and
wherein the first side wall comprises a plurality of pillars.
2. The light-emitting device according to claim 1 , wherein a thickness of the dislocation stop layer is between 10 Å and 100 Å.
3. The light-emitting device according to claim 1 , wherein the dislocation layer comprises Alx1Ga1−x1N, and 0.05<x1<0.1.
4. The light-emitting device according to claim 1 , wherein the second semiconductor stack comprises a first semiconductor layer, an active layer on the first semiconductor layer and a second semiconductor layer on the active layer.
5. The light-emitting device according to claim 4 , wherein an Al concentration of the dislocation stop layer is higher than 10 times an Al concentration of the first semiconductor layer.
6. The light-emitting device according to claim 1 , wherein the first side wall comprises a side wall of the dislocation stop layer.
7. The light-emitting device according to claim 6 , the first side wall comprises an upper side wall and a lower side wall between the upper side wall and the top surface, wherein the lower side wall and the second portion of the top surface form the acute angle α between thereof.
8. The light-emitting device according to claim 7 , wherein the upper side wall comprises the side wall of the dislocation stop layer.
9. The light-emitting device according to claim 7 , wherein an angle between the upper side wall and the second portion of the top surface is larger than the acute angle α.
10. The light-emitting device according to claim 1 , further comprising:
a buffer layer between the dislocation stop layer and the top surface; and
an undoped layer between the buffer layer and the dislocation stop layer,
wherein the buffer layer comprises GaN or AlN.
11. The light-emitting device according to claim 1 , wherein a thickness of the first semiconductor stack is between 5 μm and 9 μm.
12. The light-emitting device according to claim 1 , wherein a thickness of the second semiconductor stack is between 1 μm and 7 μm.
13. The light-emitting device according to claim 1 , wherein the substrate comprises a plurality of first concavo-convex structures on the first portion and a plurality of second concavo-convex structures on the second portion and not covered by the first semiconductor stack;
wherein the second concavo-convex structures have smaller size than that of the first concavo-convex structures.
14. The light-emitting device according to claim 1 , wherein in a top view, the second portion surrounds the first portion.
15. The light-emitting device according to claim 1 , wherein in a top view, a ratio of an area of the second portion to an area of the top surface is between 0.02 and 0.35.
16. The light-emitting device according to claim 1 , wherein the top surface further comprises an edge, and the second portion is between the edge and the first portion, and a shortest distance between the first portion and the edge is between 1 μm and about 25 μm.
17. The light-emitting device according to claim 1 , further comprising a first electrode, wherein the first doped layer comprises the portion of the first upper surface, the first electrode is formed on the portion of the first upper surface and ohmic contacting the first semiconductor stack and a second electrode formed on the second semiconductor stack and ohmic contacting the second semiconductor stack;
wherein in a top view, the first upper surface comprises a first edge, a second edge opposite to the first edge, a third edge and a fourth edge opposite to the third edge;
wherein the first electrode comprises a first bonding pad near the first edge and a first finger extending along the third edge; and
wherein the second electrode comprises a second bonding pad near the second edge and a second finger extending toward the first edge.
18. The light-emitting device according to claim 1 , wherein a width of one of the pillars is between 1 μm and 10 μm.
19. The light-emitting device according to claim 1 , wherein the second side wall and the portion of the first upper surface form an obtuse angle β between thereof, and wherein 100°≤β≤170°.
20. The light-emitting device according to claim 1 , wherein 30°≤α≤80°.