Semiconductor light emitting device with light extraction structures
View Patent ↗Structures are incorporated into a semiconductor light emitting device which may increase the extraction of light emitted at glancing incidence angles. In some embodiments, the device includes a low index material that directs light away from the metal contacts by total internal reflection. In some embodiments, the device includes extraction features such as cavities in the semiconductor structure which may extract glancing angle light directly, or direct the glancing angle light into smaller incidence angles which are more easily extracted from the device.
1. A device comprising:
a semiconductor structure comprising a light emitting layer disposed between an n-type region and a p-type region, wherein light exits a top side of the semiconductor structure through the n-type region;
a reflective metal contact disposed on a bottom side of the semiconductor structure and electrically connected to the p-type region; and
an oxide disposed between the reflective metal contact and the p-type region, wherein light generated internal to the semiconductor structure at less than a certain angle is reflected off the oxide by total internal reflection toward the top side, and wherein light generated internal to the semiconductor structure passing through the oxide is reflected toward the top side by the reflective metal contact;
wherein at least a portion of the top side of the semiconductor structure is textured.
2. The device of claim 1 wherein a distance between the textured portion of the top side of the semiconductor structure and the reflective metal contact is less than 5 μm.
3. The device of claim 1 wherein a difference between an index of refraction of the oxide and an index of refraction of the p-type region is at least 0.4.
4. The device of claim 1 wherein the oxide is doped.
5. The device of claim 1 wherein the oxide is indium tin oxide.
6. The device of claim 1 wherein the oxide is one of InO, ZnO, Ga x O y , and CuO.
7. The device of claim 1 further comprising a metal layer disposed between the semiconductor structure and the oxide.
8. The device of claim 1 wherein the oxide is porous.
9. The device of claim 1 wherein the oxide comprises columns with air gaps between the columns.
10. The device of claim 1 wherein the oxide has a resistance no more than 1 Ω-cm.
11. The device of claim 1 wherein the p-type region is a first p-type region, the device further comprising a second p-type region, wherein the oxide is disposed between the first p-type region and the second p-type region.
12. The device of claim 11 wherein the oxide is formed in a plurality of regions, the device further comprising AlInN disposed between neighboring oxide regions.
13. The device of claim 11 wherein the oxide is formed in a plurality of regions and the second p-type region is patterned to form openings aligned with the oxide regions.
14. The device of claim 11 wherein the second p-type region is disposed between the oxide and the reflective metal.
15. The device of claim 11 wherein the oxide is one of amorphous Al x O y and amorphous Al x In y O z .