Omnidirectional reflector

• US 8,415,691 B2
• Filed: 08/29/2008
• Issued: 04/09/2013
• Est. Priority Date: 08/18/2008
• Status: Active Grant

• Current Assignee: Epistar Corporation (Ennostar, Inc.)
• Original Assignee: TSMC Solid State Lighting Ltd. (Ennostar, Inc.)
• Inventors: Chen, Ding-Yuan, Yu, Chen-Hua, Chiou, Wen-Chih
• Primary Examiner(s): Stark, Jarrett
• Assistant Examiner(s): TYNES JR., LAWRENCE C
• Application Number:
  US12/202,167
• Publication Number:
  US 20100038659A1
• Time in Patent Office: 1,684 Days
• Field of Search: 257/98, 257/603
• US Class Current: 257/98
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

A system and method for manufacturing an LED is provided. A preferred embodiment includes a substrate with a distributed Bragg reflector formed over the substrate. A photonic crystal layer is formed over the distributed Bragg reflector to collimate the light that impinges upon the distributed Bragg reflector, thereby increasing the efficiency of the distributed Bragg reflector. A first contact layer, an active layer, and a second contact layer are preferably either formed over the photonic crystal layer or alternatively attached to the photonic crystal layer.

Claims

1. A light-generating device comprising:

a substrate;

a reflective layer over the substrate;

a photonic crystal collimator layer different from the reflective layer disposed over the reflective layer, the photonic crystal collimator layer comprising a first homogenous material that extends through the photonic crystal collimator layer in a direction perpendicular to the substrate; and

a light-emitting diode over the photonic crystal collimator layer, wherein the light-emitting diode is in direct physical contact with the photonic crystal collimator layer.

2. The light-generating device of claim 1, further comprising a metal bonding layer between the photonic crystal collimator layer and the light-emitting diode.

3. The light-generating device of claim 1, wherein the photonic crystal collimator layer is substantially thicker than the reflective layer.

4. The light-generating device of claim 1, wherein the reflective layer comprises a distributed Bragg reflector.

5. The light-generating device of claim 1, wherein the photonic crystal collimator layer comprises a lattice of a first material located within a second material, the second material having a different refractive index than the first material.

6. The light-generating device of claim 1, wherein the photonic crystal collimator layer is homogenous in a first direction and non-homogenous in a second direction and a third direction.

7. The light-generating device of claim 1, wherein the photonic crystal collimator layer comprises GaN, Si or dielectric materials.

8. A light-generating device comprising:

a substrate;

a reflective layer over the substrate;

a collimator over the reflective layer, the collimator comprising a first material and a second material extending away from the substrate through the first material, wherein the reflective layer and the collimator have different material compositions; and

a light-emitting diode over the collimator, wherein the light-emitting diode is in direct physical contact with the collimator.

9. The light-generating device of claim 8, further comprising a metal layer between the collimator and the light-emitting diode.

10. The light-generating device of claim 8, wherein the collimator is substantially thicker than the reflective layer.

11. The light-generating device of claim 8, wherein the reflective layer comprises a distributed Bragg reflector.

12. The light-generating device of claim 8, wherein the collimator is substantially homogenous in a first direction substantially perpendicular to a surface of the collimator and non-homogenous in a second direction and as third direction, the second direction and the third direction being substantially parallel to the surface of the collimator.

13. The light-generating device of claim 8, wherein the collimator comprises GaN, Si or dielectric materials.

14. A light-emitting device comprising:

a first substrate;

a light-emitting diode over the first substrate; and

a reflector located between the light-emitting diode and the first substrate, the reflector comprising;

a reflective layer; and

a photonic crystal layer different from the reflective layer, wherein the photonic crystal layer is a collimator and comprises a plurality of columns formed through a base material, the plurality of columns comprising a column material different from the base material

wherein the reflector is in direct physical contact with the light-emitting diode.

15. The light-emitting device of claim 14, wherein the photonic crystal layer is located between the reflective layer and the light-emitting diode.

16. The light-emitting device of claim 15, wherein the photonic crystal layer is at least multiple times thicker than the reflective layer.

17. The light-emitting device of claim 14, wherein the reflective layer comprises a distributed Bragg reflector.

18. The light-emitting device of claim 14, wherein the photonic crystal layer comprises GaN, Si or dielectric materials.

19. The light-emitting device of claim 14, further comprising a layer of metal between the photonic crystal layer and the light-emitting diode.

20. The light-emitting device of claim 14, wherein the photonic crystal layer is homogenous in a first direction and non-homogenous in a second direction and a third direction.