Light emitting diode with structured substrate
View Patent ↗Embodiments of the invention include a semiconductor light emitting device. The device includes a substrate having a first surface and a second surface opposite the first surface. The device further includes a semiconductor structure disposed on the first surface of the substrate. A cavity is disposed within the substrate. The cavity extends from the second surface of the substrate. The cavity has a sloped side wall.
1. A semiconductor light emitting device comprising:
a substrate having a first surface and a second surface opposite the first surface;
a semiconductor structure disposed on the first surface of the substrate, the semiconductor structure comprising a light emitting region sandwiched between n- and p-type regions, an n-contact connected to the n-type region, and a p-contact connected to the p-type region, the n- and p-contacts formed on the surface of the semiconductor structure opposite the first surface;
a hollow disposed in the substrate, the hollow extending from the second surface of the substrate, the hollow having a sloped side wall; and
a high refractive index material disposed over the n- and p-contacts, the high refractive index material having a refractive index of at least 1.5.
2. The semiconductor light emitting device of claim 1 wherein:
the substrate has a thickness in a first direction, the first direction being perpendicular to the first and second surfaces; and
a deepest part of the hollow measured in the first direction is at least 70% of the thickness of the substrate in the first direction.
3. The semiconductor light emitting device of claim 1 wherein the hollow comprises at least 50% of a volume comprising the volume of the hollow plus the volume of the substrate.
4. The semiconductor light emitting device of claim 1 wherein:
the semiconductor light emitting device is rectangular; and
a thickness of the substrate at a thickest point of the substrate is at least 90% of a length of a short side of the rectangular semiconductor light emitting device.
5. The semiconductor light emitting device of claim 1 wherein an angle between the sloped side wall of the hollow and a plane perpendicular to the first surface is no more than 30°.
6. The semiconductor light emitting device of claim 1 wherein the first surface is textured.
7. The semiconductor light emitting device of claim 1 , wherein a majority of light emitted from the light emitting region is extracted into the substrate.
8. The semiconductor light emitting device of claim 1 , wherein light emitted from the light emitting region is extracted out of the semiconductor light emitting device through sides of the substrate and sides of the semiconductor structure.
9. The semiconductor light emitting device of claim 1 , wherein the semiconductor light emitting device is a die having four sides at outer edges of the die, each side connecting the second surface of the substrate with the high refractive index material, and the hollow extends along an entire length of the die between two opposite sides of the die.
10. The semiconductor light emitting device of claim 1 , wherein the sloped sidewall of the hollow is coated with a reflective material.
11. The semiconductor light emitting device of claim 1 , wherein the hollow is filled with a thermally conductive material.
12. The semiconductor light emitting device of claim 1 wherein the hollow has a triangular cross section along a first axis.
13. The semiconductor light emitting device of claim 12 wherein the hollow has a triangular cross section along a second axis perpendicular to the first axis.
14. The semiconductor light emitting device of claim 13 wherein the semiconductor light emitting device is square.
15. The semiconductor light emitting device of claim 1 further comprising:
a transparent, conductive material disposed between the semiconductor structure and the high refractive index material.
16. The semiconductor light emitting device of claim 15 wherein a surface of the high refractive index material opposite the transparent conductive material is textured.
17. The semiconductor light emitting device of claim 16 wherein the textured surface of the high refractive index material comprises a plurality of 3-sided pyramids arranged in a lattice.
18. A semiconductor light emitting device comprising
a substrate having a first surface and a second surface opposite the first surface;
a semiconductor structure disposed on the first surface of the substrate, the semiconductor structure comprising a light emitting region sandwiched between n- and p-type regions, an n-contact connected to the n-type region, and a p-contact connected to the p-type region;
a hollow disposed in the substrate, the hollow extending from the second surface of the substrate, the hollow having a sloped side wall;
a lens disposed over the semiconductor structure and the substrate, and extending along sidewalls of the semiconductor structure and the substrate; and
a gap disposed between the semiconductor structure and the lens.
19. The semiconductor light emitting device of claim 18 , wherein the gap extends between the lens and the sidewalls of the semiconductor structure and the substrate.
20. The semiconductor light emitting device of claim 18 , wherein the lens completely surrounds the semiconductor structure and the substrate above the second surface.