GaN-based LED
A GaN-based LED includes: a substrate with front and back sides; an epitaxial layer formed over the front side of the substrate and including, from top down, a P-type layer, a light-emitting area, and an N-type layer; a current spreading layer formed over the P-type layer; a P electrode formed over the current spreading layer; a first reflecting layer between the current spreading layer and the epitaxial layer, disposed at a peripheral area of the epitaxial layer in a band-shaped distribution; and a second reflecting layer over the back side the substrate. The band-shaped or annular distribution can increase a probability light extraction of the LED sideways. By controlling the ratio of lights extracted upwards and sideways, the light-emitting distribution evenness can be adjusted and the uneven heat dissipation can be improved.
1. A GaN-based LED, comprising:
a substrate with front and back sides;
an epitaxial layer formed over the front side of the substrate and including, from top down, a P-type layer, a light-emitting area, and an N-type layer;
a current spreading layer formed over the P-type layer;
a P electrode formed over the current spreading layer;
a first reflecting layer between the current spreading layer and the epitaxial layer, disposed at a peripheral area of the epitaxial layer in a band-shaped distribution, and configured to reflect a portion of light emitted upward from the light-emitting area toward at least two sides of the LED to increase light extraction sideways and thereby improve a light distribution evenness; and
a second reflecting layer over the back side the substrate.
2. The GaN-based LED of claim 1 , further comprising a third reflecting layer between the current spreading layer and the P electrode, underneath the P electrode.
3. The GaN-based LED of claim 1 , wherein the first reflecting layer has a closed annular shape.
4. The GaN-based LED of claim 1 , wherein the P electrode is disposed at a peripheral area of the current spreading layer, and wherein the first reflecting layer is disposed away from the P electrode.
5. The GaN-based LED of claim 1 , wherein a width of the first reflecting layer is 5-30 μm.
6. The GaN-based LED of claim 1 , wherein the first reflecting layer has an area of 5%-30% of the light-emitting area of the epitaxial layer.
7. The GaN-based LED of claim 2 , wherein a diameter of the third reflecting layer is 50-200 μm.
8. The GaN-based LED of claim 1 , wherein the first reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.
9. The GaN-based LED of claim 1 , wherein the second reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.
10. The GaN-based LED of claim 2 , wherein the third reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.
11. A light-emitting system comprising a plurality of GaN-based LEDs, each LED comprising:
a substrate with front and back sides;
an epitaxial layer formed over the front side of the substrate and including, from top down, a P-type layer, a light-emitting area, and an N-type layer;
a current spreading layer formed over the P-type layer;
a P electrode formed over the current spreading layer;
a first reflecting layer between the current spreading layer and the epitaxial layer, disposed at a peripheral area of the epitaxial layer in a band-shaped distribution, and configured to reflect a portion of light emitted upwards from the light-emitting area toward at least two sides of the LED to increase light extraction sideways and thereby improve a light distribution evenness; and
a second reflecting layer over the back side the substrate.
12. The system of claim 11 , each LED further comprising a third reflecting layer between the current spreading layer and the P electrode, underneath the P electrode.
13. The system of claim 11 , wherein the first reflecting layer has a closed annular shape.
14. The system of claim 11 , wherein the P electrode is disposed at a peripheral area of the current spreading layer, and wherein the first reflecting layer is disposed away from the P electrode.
15. The system of claim 11 , wherein a width of the first reflecting layer is 5-30 μm.
16. The system of claim 11 , wherein the first reflecting layer has an area of 5%-30% of the light-emitting area of the epitaxial layer.
17. The system of claim 12 , wherein a diameter of the third reflecting layer is 50-200 μm.
18. The system of claim 11 , wherein the first reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.
19. The system of claim 11 , wherein the second reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.
20. The system of claim 12 , wherein the third reflecting layer comprises one of a DBR, a metal reflecting layer, or an ODR.