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 method for fabricating a light-emitting diode (LED) chip, the method comprising:
providing an active LED structure comprising an active layer between an n-type layer and a p-type layer;
providing a first reflective layer adjacent the active LED structure;
providing an adhesion layer by depositing a metal layer on the first reflective layer and anodizing the metal layer to form an anodic metal oxide, the adhesion layer forming a plurality of openings; and
providing a second reflective layer on the adhesion layer and within the plurality of openings.
2. The method of claim 1 , wherein anodizing the metal layer comprises anodizing with an electrolytic solution.
3. The method of claim 1 , wherein the metal layer comprises aluminum and the anodic metal oxide comprises anodic aluminum oxide.
4. The method of claim 3 , wherein the anodic aluminum oxide comprises Al x O y , wherein 1≤x≤4 and 1≤y≤6.
5. The method of claim 4 , wherein the anodic aluminum oxide comprises Al x O y , wherein x=2 and y=3.
6. The method of claim 1 , wherein anodizing the metal layer comprises stopping such that one or more openings of the plurality of openings extend through less than an entire thickness of the adhesion layer.
7. The method of claim 6 , wherein the one or more openings of the plurality of openings extend from the second reflective layer toward the first reflective layer.
8. The method of claim 1 , wherein anodizing the metal layer comprises forming one or more openings of the plurality of openings through an entire thickness of the adhesion layer.
9. The method of claim 1 , wherein the adhesion layer comprises a thickness in a range of about 60 angstroms to about 150 angstroms.
10. The method of claim 1 , wherein the adhesion layer comprises a thickness in a range of about 90 angstroms to about 120 angstroms.
11. The method of claim 1 , wherein the first reflective layer comprises a dielectric layer and the second reflective layer comprises a metal reflective layer.
12. The method of claim 1 , wherein the first reflective layer comprises a plurality of dielectric layers.
13. The method of claim 12 , wherein the plurality of dielectric layers comprises an aperiodic Bragg reflector.