Reflective Layer for Light-Emitting Diodes

• US 20140235001A1
• Filed: 05/02/2014
• Published: 08/21/2014
• Est. Priority Date: 08/18/2008
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: TSMC Solid State Lighting Ltd. (Epistar Corporation)
• Inventors: Chen, Ding-Yuan, Yu, Chia-Lin, Yu, Chen-Hua, Chiou, Wen-Chih
• Granted Patent: US 9,214,613 B2
• Time in Patent Office: Days
• US Class Current: 438/29
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

A system and method for manufacturing a light-generating device is described. A preferred embodiment comprises a plurality of LEDs formed on a substrate. Each LED preferably has spacers along the sidewalls of the LED, and a reflective surface is formed on the substrate between the LEDs. The reflective surface is preferably located lower than the active layer of the individual LEDs.

Claims

1. A method of forming a light-generating device, comprising:

forming a plurality of light-emitting diodes (LEDs) over a substrate, the LEDs each including a first group III-V compound layer, a second group III-V compound layer, and an active layer disposed between the first group III-V compound layer and the second group III-V compound layer, wherein the LEDs are physically separated from one another;

forming spacers on side surfaces of each of the LEDs; and

thereafter forming a reflective material over portions of the substrate that are not covered by the LEDs and the spacers, wherein the reflective material is formed below the active layer of the LEDs.

2. The method of claim 1, further comprising:

forming a dielectric layer over the reflective material; and

forming a conductive layer over the dielectric layer and over the LEDs.

3. The method of claim 2, wherein the forming of the conductive layer is performed such that the LEDs are electrically coupled together by the conductive layer.

4. The method of claim 2, wherein the forming of the dielectric layer and the forming of the conductive layer are performed such that the dielectric layer and the conductive layer are each transparent.

5. The method of claim 4, wherein:

the dielectric layer contains silicon oxide, silicon nitride, or silicon oxynitride; and

the conductive layer contains a thin layer of nickel, a thin layer of gold, or a transparent conductive oxide.

6. The method of claim 4, wherein the conductive layer has a thickness in a range from about 10 angstroms to about 1000 angstroms.

7. The method of claim 1, wherein the forming of the plurality of LEDs comprises:

growing the first group III-V compound layer over the substrate;

growing the active layer over the first group III-V compound layer;

growing the second group III-V compound layer over the active layer; and

patterning the second group III-V compound layer, the active layer, and the first group III-V compound layer into the plurality of LEDs.

8. The method of claim 7, wherein the patterning is performed such that a lateral dimension of each LED is between about 0.3 to about 3 times a wavelength of a light emitted by said LED.

9. A method of forming a light-generating device, comprising:

forming a first group III-V compound layer over a substrate;

forming an active layer over the first group III-V compound layer;

forming a second group III-V compound layer over the active layer;

patterning the second group III-V compound layer, the active layer, and the first group III-V compound layer into a plurality of nano-sized LEDs, wherein a ratio of a lateral dimension of each nano-sized LED and a wavelength of a light emitted by the nano-sized LED is in a range from about 0.3 to about 3;

forming spacers on sidewalls of the LEDs; and

thereafter forming a reflective material over the substrate and between the spacers.

10. The method of claim 9, wherein the forming of the reflective material is performed such that a thickness of the reflective material is less than a distance between the substrate and the active layer.

11. The method of claim 9, wherein the nano-sized LEDs are separated by a plurality of gaps, and further comprising filling the gaps with a transparent material.

12. The method of claim 11, further comprising forming a top electrode layer over the transparent material and over the nano-sized LEDs, wherein the top electrode layer is electrically coupled to the nano-sized LEDs.

13. The method of claim 12, wherein the top electrode layer is formed to be transparent and have a thickness in a range from about 10 angstroms to about 1000 angstroms.

14. A method for forming a light-generating device, the method comprising:

providing a substrate;

forming a plurality of light-emitting diodes on the substrate, each of the plurality of light-emitting diodes comprising an active layer; and

forming a reflective layer on the substrate;

wherein the reflective layer is located between adjacent ones of the plurality of light-emitting diodes and below the active layers.

15. The method of claim 14, wherein the reflective layer comprises aluminum, silver, or other reflective materials.

16. The method of claim 14, wherein at least one of the plurality of light-emitting diodes is configured to emit a light with a first wavelength, the at least one of the plurality of light-emitting diodes having a width that is comparable with the first wavelength.

17. The method of claim 14, wherein the forming a reflective layer includes forming spacers along sidewalls of the plurality of light-emitting diodes.

18. The method of claim 17, further comprising filling an area between the spacers and over the reflective layer with a light-transmissive material.

19. The method of claim 18, further comprising planarizing the light-transmissive material, the planarizing step also substantially exposing top surfaces of the plurality of light-emitting diodes.

20. The method of claim 14, wherein the forming a plurality of light-emitting diodes comprises:

forming a first contact layer;

forming an active layer over the first contact layer;

forming a second contact layer over the active layer;

forming a hard mask over the second contact layer, the hard mask exposing portions of the second contact layer; and

etching the exposed portions of the second contact layer, the active layer, and the first contact layer to form the plurality of light-emitting diodes.