REFLECTIVE STRUCTURE FOR LIGHT EMITTING DEVICES

• US 20180090645A1
• Filed: 09/25/2017
• Published: 03/29/2018
• Est. Priority Date: 09/27/2016
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Inventors: Nelson, Erik C., Deb, Parijat P.
• Granted Patent: US 10,665,759 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil

Abstract

Described is a reflector for light emitting devices. A device includes a reflector in contact with a first n-type region and a second n-type region. The reflector includes multiple layers. One layer having an index of refraction different than the other layers. The device includes a light emitting region (LER) in contact with the second n-type region, a p-type region in contact with the LER and a light extraction region (LXR) in contact with the p-type region. A majority of light escapes the device through the LXR. The reflector reflects light emitted by the LER back towards the LXR. In another device, a reflector is embedded in a n-type region of the device. The device includes a LER, a p-type region, and a wavelength converter structure. The reflector reflects light emitted by the wavelength converting structure back towards the wavelength converting structure.

Claims

1. A device comprising:

a first n-type region;

a reflector in contact with the first n-type region, the reflector including a plurality of layers and at least one of the plurality of layers having an index of refraction different than other layers of the plurality of layers;

a second n-type region in contact with the reflector;

a light emitting region in contact with the second n-type region;

a p-type layer in contact with the light emitting region; and

a light extraction region in contact with the p-type region, the device having a majority of light escaping through the light extraction region,

the reflector being tuned to reflect light emitted by the light emitting region back toward the light extraction region.

2. The device of claim 1, wherein the least one layer is a first plurality of layers alternating with a second plurality of layers of the plurality of layers, the first plurality of layers being more porous than the second plurality of layers.

3. The device of claim 1, wherein the least one layer is more highly doped than the other plurality of layers.

4. The device of claim 1, wherein the least one layer is a porous semiconductor layer and the other plurality of layers are non-porous semiconductor layers.

5. The device of claim 1, wherein the at least one layer is GaN and the other layers are AlInN.

6. The device of claim 1, wherein the at least one layer is InGaN and the other layers are AlGaN.

7. A device comprising:

a n-type region;

a reflector embedded in the n-type region, the reflector including a plurality of layers and at least one of the plurality of layers having an index of refraction different than other layers of the plurality of layers;

a light emitting region in contact with the n-type region;

a p-type region in contact with the light emitting region; and

a wavelength converting structure in contact with the p-type region,

the reflector being tuned to reflect light emitted by the wavelength converting structure back toward the wavelength converting structure.

8. The device of claim 7, wherein the least one layer is a first plurality of layers alternating with a second plurality of layers of the plurality of layers, the first plurality of layers being more porous than the second plurality of layers.

9. The device of claim 7, wherein the least one layer is more highly doped than the other plurality of layers.

10. The device of claim 7, wherein the least one layer is a porous semiconductor layer and the other plurality of layers are non-porous semiconductor layers.

11. The device of claim 7, wherein the at least one layer is GaN and the other layers are AlInN.

12. The device of claim 7, wherein the at least one layer is InGaN and the other layers are AlGaN.

13. A method for making a device, the method comprising:

growing a first n-type region on a substrate;

growing a reflector on the first n-type region, the reflector including a plurality of layers and at least one of the plurality of layers having an index of refraction different than other layers of the plurality of layers;

growing a second n-type region on the reflector;

growing a light emitting region on the second n-type layer;

growing a p-type region on the light emitting region; and

growing a transparent current spreading region on the p-type region, the device having a majority of light escaping through the transparent current spreading region,

the reflector being tuned to reflect light emitted by the light emitting region back toward the transparent current spreading region.

14. The method of claim 13, wherein the least one layer is a first plurality of layers and further comprising:

alternating the first plurality of layers with a second plurality of layers of the plurality of layers, the first plurality of layers being more porous than the second plurality of layers.

15. The method of claim 13, further comprising:

doping the least one layer more highly doped than the other plurality of layers.

16. The method of claim 13, further comprising:

growing the least one layer more from a porous semiconductor material and the other plurality of layers from non-porous semiconductor materials.

17. The method of claim 13, further comprising:

growing the at least one layer from GaN and the other layers from AlInN.

18. The method of claim 13, further comprising:

growing the at least one layer from InGaN and the other layers from AlGaN.