Light emitting diode having vertical topology and method of making the same
View Patent ↗An LED having vertical topology and a method of making the same is capable of improving a luminous efficiency and reliability, and is also capable of achieving mass productivity. The method includes forming a semiconductor layer on a substrate; forming a first electrode on the semiconductor layer; forming a supporting layer on the first electrode; generating an acoustic stress wave at the interface between the substrate and semiconductor layer, thereby separating the substrate from the semiconductor layer; and forming a second electrode on the semiconductor layer exposed by the separation of the substrate.
1. A light emitting diode (LED) having vertical topology, comprising:
a semiconductor structure comprising a plurality of semiconductor layers;
a first electrode disposed on a first surface of the semiconductor structure, the first electrode comprising a reflective electrode;
a passivation layer disposed on at least one of the first electrode and the semiconductor structure;
a connection metal layer disposed on the first electrode;
a second electrode on a second surface of the semiconductor structure;
and a supporting layer disposed on the connection metal layer,
wherein the connection metal layer comprises a first metal layer electrically connected to the first electrode, a diffusion barrier layer disposed on the first metal layer, and a second metal layer disposed on the diffusion barrier layer.
2. The LED according to claim 1 , further comprising a metal layer disposed between the passivation layer and the connection metal layer.
3. The LED according to claim 1 , wherein the plurality of semiconductor layers comprise:
an n-type semiconductor layer;
an active layer disposed on the n-type semiconductor layer; and
a p-type semiconductor layer disposed on the active layer.
4. The LED according to claim 3 , further comprising a current diffusion layer comprising an InGaN layer or an InGaN/GaN superlattice layer, on the p-type semiconductor layer.
5. The LED according to claim 1 , wherein the reflective electrode comprises Ag or Al.
6. The LED according to claim 1 , wherein the reflective electrode has a thickness of more than 100 Å.
7. The LED according to claim 1 , wherein the reflective electrode comprises a third metal layer electrically connected to the semiconductor structure; a second diffusion barrier layer disposed on the third metal layer; and a fourth metal layer disposed on the second diffusion barrier layer.
8. The LED according to claim 7 , wherein the third metal layer, the second diffusion barrier layer and the fourth metal layer are formed of a single alloy layer.
9. The LED according to claim 1 , wherein the first metal layer, the diffusion barrier layer and the second metal layer are formed of a single alloy layer.
10. The LED according to claim 1 , wherein the first electrode further comprises a transparent electrode.
11. The LED according to claim 1 , further comprising a light-extraction structure on the second surface of the semiconductor structure.
12. The LED according to claim 11 , wherein the light-extraction structure comprises a photonic crystal structure.
13. The LED according to claim 12 , wherein the photonic crystal structure has a period of 0.2 to 2 μm.
14. The LED according to claim 12 , wherein the photonic crystal structure comprises a pattern having a six-fold(60°) or twelve-fold(30°) rotational symmetry.
15. The LED according to claim 14 , wherein the pattern comprises a unit cell having 19 holes, and wherein the unit cell shares 6 of 19 holes with adjacent unit cells.
16. The LED according to claim 15 , wherein the 19 holes have a distribution having 1 hole in the center of the cell, 6 holes therearound, arranged at the same intervals, and 12 holes arranged at the same intervals around the 6 holes.
17. The LED according to claim 12 , wherein the photonic crystal structure has a translational symmetry.
18. The LED according to claim 1 , wherein the supporting layer comprises a side rim protion for supporting a lateral side of the semiconductor structure, via contact with the connection metal layer.
19. The LED according to claim 1 , wherein the passivation layer comprises at least one of silicon dioxide (SiO 2 ), photoresist (PR), SOG and polyimide.
20. A light emitting diode (LED) having vertical topology, comprising:
a semiconductor structure comprising a plurality of semiconductor layers;
a first electrode disposed on a first surface of the semiconductor structure and comprising at least two layers;
a light-extraction structure on at least a portion of a second surface of the semiconductor structure, the light-extraction structure including a first photonic crystal structure that includes randomly positioned unit structures, wherein the light-extraction structure reflects a second photonic crystal structure including periodically positioned unit structures, and wherein the distance between the periodically positioned unit structures substantially equals the average distance between the randomly positioned unit structures;
a second electrode disposed on the second surface of the semiconductor structure; and
a supporting layer disposed on the first electrode.
21. The LED according to claim 20 , further comprising:
a current diffusion layer between the first surface of the semiconductor structure and the first electrode.
22. The LED according to claim 20 , wherein the light-extraction structure comprises a photonic crystal structure having a plurality of holes, wherein the diameter of the hole is in the range of 0.1 A to 0.9 A (where, A is the period of the photonic crystal structure), and the depth of the hole is in the range of 0.1 μm to 5 μm.
23. The LED according to claim 20 , further comprising:
a current diffusion layer comprising an InGaN layer or an InGaN/GaN superlattice layer between the first surface of the semiconductor structure and the first electrode.
24. The LED according to claim 1 , wherein the connection metal layer contacts the passivation layer.
25. The LED according to claim 1 , wherein the first electrode is formed integrally with the connection metal layer.
26. The LED according to claim 1 , wherein the connection metal layer comprises a seed metal for formation of the supporting layer or a bonding metal for attaching the supporting layer.
27. The LED according to claim 1 , wherein the first electrode comprises a transparent conductive oxide layer.
28. The LED according to claim 20 , further comprising a connection metal layer disposed between the first electrode and the supporting layer.
29. The LED according to claim 28 , wherein the connection metal layer comprises a seed metal for formation of the supporting layer or a bonding metal for attaching the supporting layer.
30. The LED according to claim 28 , wherein the first electrode is formed integrally with the connection metal layer.
31. The LED according to claim 20 , wherein the supporting layer comprises a side rim portion for supporting a lateral side of the semiconductor structure.
32. The LED according to claim 20 , wherein the first electrode comprises a transparent conductive oxide layer.
33. The LED according to claim 1 , wherein the connection metal layer directly contacts and is disposed between the first electrode and the supporting layer.