Reflective layers for light-emitting diodes
A light-emitting diode (LED) chip with reflective layers having high reflectivity is disclosed. 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. An adhesion layer may be provided between the first reflective layer and the second reflective layer. The adhesion layer may comprise a metal oxide that promotes improved adhesion with reduced optical losses.
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;
a second reflective layer on the first reflective layer; and
an adhesion layer between the first reflective layer and the second reflective layer, wherein the adhesion layer comprises a metal oxide, wherein the adhesion layer forms a plurality of openings that extend through the adhesion layer, and one or more openings of the plurality of openings are at least partially filled by the second reflective layer.
2. The LED chip of claim 1 wherein the metal oxide comprises aluminum oxide.
3. The LED chip of claim 2 wherein the aluminum oxide comprises Al x O y , wherein 1≤x≤4 and 1≤y≤6.
4. The LED chip of claim 2 wherein the aluminum oxide comprises Al x O y , wherein x=2 and y=3.
5. The LED chip of claim 1 wherein the metal oxide comprises an anodic metal oxide.
6. The LED chip of claim 5 wherein the anodic metal oxide comprises anodic aluminum oxide.
7. The LED chip of claim 1 wherein the adhesion layer comprises a thickness in a range of about 60 angstroms to about 150 angstroms.
8. The LED chip of claim 1 wherein the adhesion layer comprises a thickness in a range of about 90 angstroms to about 120 angstroms.
9. The LED chip of claim 1 wherein each dielectric layer of the plurality of dielectric layers comprises a different thickness.
10. The LED chip of claim 1 wherein the plurality of dielectric layers comprises from 5 to 13 dielectric layers.
11. The LED chip of claim 1 wherein the plurality of dielectric layers comprises an aperiodic Bragg reflector.
12. The LED chip of claim 1 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.
13. The LED chip of claim 1 wherein the plurality of dielectric layers comprises alternating first dielectric layers and second dielectric layers.
14. The LED chip of claim 13 wherein the first dielectric layers comprise silicon dioxide and the second dielectric layers comprise silicon nitride.
15. The LED chip of claim 14 wherein the silicon nitride comprises a refractive index in a range from about 1.8 to about 2.2.
16. The LED chip of claim 14 wherein the silicon nitride comprises a refractive index in a range from about 2.0 to about 2.2.
17. 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;
a second reflective layer on the first reflective layer; and
an adhesion layer between the first reflective layer and the second reflective layer, wherein the adhesion layer comprises an anodic metal oxide, wherein the adhesion layer forms a plurality of openings that extend through the adhesion layer, and one or more openings of the plurality of openings are at least partially filled by the second reflective layer.
18. The LED chip of claim 17 wherein the anodic metal oxide comprises anodic aluminum oxide.
19. The LED chip of claim 18 wherein the anodic aluminum oxide comprises a refractive index in a range from about 1.4 to about 2.1.
20. The LED chip of claim 17 wherein the plurality of openings extend through an entire thickness of the adhesion layer.
21. The LED chip of claim 17 wherein the plurality of openings extend through less than an entire thickness of the adhesion layer.
22. The LED chip of claim 21 wherein the plurality of openings extend from the second reflective layer toward the first reflective layer.
23. The LED chip of claim 17 wherein the adhesion layer comprises a thickness in a range of about 60 angstroms to about 150 angstroms.
24. The LED chip of claim 1 wherein the plurality of openings extend through an entire thickness of the adhesion layer.
25. The LED chip of claim 1 wherein the plurality of openings extend through less than an entire thickness of the adhesion layer.