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;
a reflective metal contact disposed on a bottom side of the semiconductor structure and electrically connected to the p-type region;
a material disposed between at least a portion of the reflective metal contact and the p-type region, wherein a difference between an index of refraction of the material and an index of refraction of the p-type region is at least 0.4;
wherein:
at least a portion of a top side of the semiconductor structure is textured; and
a distance between the textured portion of the top side of the semiconductor structure and the reflective metal contact is less than 5 μm.
2. The device of claim 1 wherein a difference between an index of refraction of he material and an index of refraction of the p-type region is at least 0.7.
3. The device of claim 1 wherein:
the light emitting layer comprises a III-nitride material;
and the reflective metal contact comprises silver.
4. The device of claim 1 wherein the material is one of a dielectric, an oxide, a semiconductor, Si0 2 , SiN, Ti0 2 , Ah0 3 , ITO, InO, ZnO, CuO, AlInGaN, AlGaN, AlInN, Al x O y , Ga x O y and Al x In y O z .
5. The device of claim 1 wherein an interface between the semiconductor structure and the material is configured to reflect light incident on the interface at angles greater than 70° relative to a normal to a major plane of the light emitting layer.
6. The device of claim 1 wherein a composite reflectivity of the material and the reflective metal contact on the p-type region is greater than a reflectivity of the reflective metal contact in direct contact with the p-type region.
7. The device of claim 1 wherein the material is configured such that a round-trip loss in the material is less than a loss of a visible spectrum wave reflecting off the reflective metal contact in direct contact with the p-type region.
8. The device of claim 1 wherein the textured portion is one of randomly roughened and patterned with a photonic crystal.
9. The device of claim 1 wherein the reflective contact directly contacts the semiconductor structure through openings formed in the material.
10. The device of claim 9 wherein nearest neighbor openings are spaced less than 2 μm apart.
11. The device of claim 1 wherein a thickness of the material is less than 500 μm.