Nanocone arrays for enhancing light outcoupling and package efficiency
An LED structure includes an epi layer grown on a substrate and a plurality of dielectric nanoantennas positioned within the epi layer. The dielectric antennas can be periodically arranged to reduce reabsorption of light and redirect oblique incident light to improve overall light coupling efficiency. Each of the dielectric nanoantennas can have a top, a bottom, a height less than 1000 nm and greater than 200 nm and a diameter less than 2000 nm and greater than 300 nm.
1. An LED structure, comprising
a substrate with a first patterned surface;
a first epi layer of GaN grown on the first patterned surface of the substrate and comprising a second patterned surface forming an interface with the first patterned surface of the substrate, the interface arranged to increase outcoupling of light travelling through the epi layer into the substrate;
an active region in direct contact with the first epi layer;
a first plurality of dielectric nanoantennas arranged to form more than one plane, the first plurality of dielectric nanoantennas positioned within the first epi layer between the active region and substrate and spaced apart from the interface, each of the first plurality of dielectric nanoantennas having a blunt end facing the interface and comprising a core material and a shell material, a narrower end opposite the blunt end facing away from the interface with a narrower diameter than the blunt end and comprising of the shell material, and at least one side surface connecting the blunt end and the narrower end and consisting of the shell material, each of the blunt end, the narrower end, and the at least one side surface being in direct contact with the first epi layer, the first plurality of dielectric nanoantennas arranged to allow transmission of light travelling through the epi layer into the substrate;
a contact layer on an opposite side of the first epi layer from the substrate;
a tunnel junction layer adjacent to the active region;
a second epi layer positioned on an opposite side of the active region from the first epi layer to be between the active region and the contact layer; and
a second plurality of dielectric nanoantennas arranged within the second epi layer to form more than one plane, each of the second plurality of dielectric nanoantennas having a blunt end facing the interface and a narrower end opposite the blunt end facing away from the interface with a narrower diameter than the blunt end.
2. The structure of claim 1 , wherein each of the first and second plurality of dielectric nanoantennas has a height less than 1000 nm and a base diameter less than 2000 nm.
3. The structure of claim 1 , wherein the dielectric nanoantennas are arranged to reflect more light via the blunt end than the narrower end.
4. The structure of claim 1 , wherein at least some of the first plurality of dielectric nanoantennas define a periodic pattern in a plane having a periodic spacing different from that of the second plurality of dielectric nanoantennas.
5. The structure of claim 1 , further comprising a second active region between the second epi layer and the contact layer.
6. The structure of claim 1 , wherein the contact layer is mirrored.
7. The structure of claim 1 , wherein the first plurality of dielectric nanoantennas collimates at least some of the light travelling through the epi layer into the substrate.
8. The structure of claim 1 , wherein the first plurality of dielectric nanoantennas are arranged to allow at least a 10% different in transmission of light travelling through the epi layer into the substrate compared to light travelling into the epi layer from the substrate back through the epi layer, for at least some angles of incidence.
9. The structure of claim 1 , wherein the contact layer is non-mirrored.
10. The structure of claim 1 , wherein each of the more than one plane of the first nanoantennas has a same periodic spacing as the more than one plane of the second nanoantennas.
11. The structure of claim 1 , wherein each of the more than one plane of the first nanoantennas has a different periodic spacing as the more than one plane of the second nanoantennas.
12. The structure of claim 1 , wherein each of the more than one plane of the first nanoantennas has a different periodic spacing as the more than one plane of the second nanoantennas.
13. The structure of claim 1 , wherein each of the first nanoantennas has a different height than each of the second nanoantennas.
14. The structure of claim 1 , wherein each of the first nanoantennas has a different width than each of the second nanoantennas.
15. The structure of claim 1 , wherein each of the first nanoantennas has a different material than each of the second nanoantennas.
16. The structure of claim 1 , wherein the second epi layer is in direct contact with the contact layer.
17. The structure of claim 1 , wherein the second epi layer is not in direct contact with the contact layer.
18. The structure of claim 1 , wherein the substrate is sapphire.
19. The structure of claim 1 , wherein the blunt end of each of the first dielectric nanoantennas is a flat circular base.
20. The structure of claim 1 , wherein the first dielectric nanoantennas are conical in shape.