Reflective layers for light-emitting diodes
A light-emitting diode (LED) chip with reflective layers having high reflectivity. The LED chip may include an active LED structure including an active layer between an n-type layer and a p-type layer. A first reflective layer is adjacent the active LED structure and comprises a plurality of dielectric layers with varying optical thicknesses. The plurality of dielectric layers may include a plurality of first dielectric layers and a plurality of second dielectric layers of varying thicknesses and compositions. The LED chip may further include a second reflective layer that includes an electrically conductive path through the first reflective layer.
1. A light-emitting diode (LED) chip comprising:
an active LED structure comprising an active layer between an n-type layer and a p-type layer;
a first reflective layer adjacent the active LED structure and comprising a plurality of dielectric layers that forms an aperiodic Bragg reflector;
a second reflective layer on the first reflective layer;
a barrier layer on the second reflective layer;
a passivation layer on the barrier layer; and
a metal-containing interlayer embedded within the passivation layer, wherein the metal-containing interlayer is electrically isolated from the active LED structure.
2. The LED chip of claim 1 wherein each dielectric layer of the plurality of dielectric layers comprises a different thickness.
3. The LED chip of claim 1 wherein the plurality of dielectric layers comprises from 7 to 13 dielectric layers.
4. The LED chip of claim 2 wherein a thickest dielectric layer of the plurality of dielectric layers is spaced from the active LED structure by at least one thinner dielectric layer.
5. The LED chip of claim 2 wherein the plurality of dielectric layers comprises alternating first dielectric layers and second dielectric layers.
6. The LED chip of claim 5 wherein the plurality of dielectric layers comprises an uneven number of first dielectric layers and an even number of second dielectric layers.
7. The LED chip of claim 5 wherein the first dielectric layers comprise silicon dioxide and the second dielectric layers comprise silicon nitride.
8. The LED chip of claim 1 wherein the second reflective layer comprises an electrically conductive material.
9. The LED chip of claim 8 wherein the second reflective layer comprises an electrically conductive path through the first reflective layer.
10. The LED chip of claim 1 further comprising a current-spreading layer between the active LED structure and the first reflective layer.
11. The LED chip of claim 10 wherein the current-spreading layer comprises indium tin oxide.
12. The LED chip of claim 1 further comprising an adhesion layer between the first reflective layer and the second reflective layer.
13. The LED chip of claim 1 further comprising a substrate wherein the n-type layer is between the substrate and the active layer.
14. The LED chip of claim 13 wherein the substrate comprises a patterned surface adjacent the n-type layer.
15. The LED chip of claim 13 further comprising a lumiphoric layer on the substrate.
16. The LED chip of claim 1 wherein the active LED structure comprises a mesa sidewall and the first reflective layer extends along the mesa sidewall.
17. The LED chip of claim 1 further comprising a submount wherein the p-type layer is between the submount and the active layer.
18. The LED chip of claim 17 further comprising a lumiphoric layer on the n-type layer.
19. A light-emitting diode (LED) chip comprising:
an active LED structure comprising an active layer between an n-type layer and a p-type layer; and
a first reflective layer adjacent the active LED structure and comprising a plurality of first dielectric layers that directly alternate with a plurality of second dielectric layers wherein each layer of the plurality of first dielectric layers comprises a different thickness;
wherein a thickest layer of the plurality of first dielectric layers is between other layers of the plurality of first dielectric layers and a thinnest layer of the plurality of first dielectric layers is arranged farthest away from the active LED structure than other layers of the plurality of first dielectric layers, the thickest layer of the plurality of first dielectric layers being at least four times thicker than any other first dielectric layer of the plurality of first dielectric layers.
20. The LED chip of claim 19 wherein the first reflective layer comprises an uneven number of the plurality of first dielectric layers compared with a number of the plurality of second dielectric layers.
21. The LED chip of claim 19 further comprising a second reflective layer on the first reflective layer.
22. The LED chip of claim 21 wherein the second reflective layer comprises an electrical path through the first reflective layer.
23. The LED chip of claim 19 further comprising a current-spreading layer between the active LED structure and the first reflective layer.
24. The LED chip of claim 23 wherein the current-spreading layer comprises indium tin oxide.
25. The LED chip of claim 21 further comprising an adhesion layer between the first reflective layer and the second reflective layer.
26. The LED chip of claim 19 wherein the first reflective layer is adjacent the p-type layer.
27. The LED chip of claim 19 wherein the active LED structure comprises a mesa sidewall and the first reflective layer extends along the mesa sidewall.
28. The LED chip of claim 1 wherein the passivation layer comprises silicon nitride.
29. The LED chip of claim 1 wherein the passivation layer comprises silicon nitride and the metal-containing interlayer comprises aluminum.
30. The LED chip of claim 1 wherein the metal-containing interlayer is electrically isolated from other portions of the LED chip by the passivation layer.
31. A light-emitting diode (LED) chip comprising:
an active LED structure comprising an active layer between an n-type layer and a p-type layer;
a first reflective layer adjacent the active LED structure and comprising a plurality of first dielectric layers and a plurality of second dielectric layers, wherein each layer of the plurality of first dielectric layers comprises a different thickness; and
a second reflective layer adjacent the first reflective layer such that the first reflective layer is between the active LED structure and the second reflective layer;
wherein a thickest layer of the plurality of first dielectric layers is between other layers of the plurality of first dielectric layers, and the thickest layer of the plurality of first dielectric layers is at least four times thicker than any other first dielectric layer of the plurality of first dielectric layers that is between the thickest layer of the plurality of first dielectric layers and the second reflective layer.
32. The LED chip of claim 31 further comprising an adhesion layer between the first reflective layer and the second reflective layer.