High reflectivity mirrors and method for making same

• US 9,362,459 B2
• Filed: 09/02/2009
• Issued: 06/07/2016
• Est. Priority Date: 09/02/2009
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: United States Department of Energy
• Inventors: Heikman, Sten, Jacob-Mitos, Matthew, Li, Ting, Ibbetson, James
• Primary Examiner(s): YUSHINA, GALINA G
• Application Number:
  US12/553,025
• Publication Number:
  US 20110049546A1
• Time in Patent Office: 2,470 Days
• Field of Search: 257 12- 15, 257/79, 257 81- 90, 257/94, 257/96, 257/98, 257/103, 257/183, 257/189, 257/198, 257/200, 257/414, 257/431, 257/432, 257/798, 257/E51.018, 257/E31.01, 257/E33.01, 257/E33.023, 257/E33.025, 257/E33.027
• US Class Current: 1/1
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/00 Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof H10K50/00 takes precedence; devices consisting of a plurality of semiconductor components formed in or on a common substrate and including semiconductor components having potential barriers, specially adapted for light emission H01L27/15; semiconductor lasers H01S5/00
• CPC Class Codes: H01L 33/0062 for devices with an active region comprising only III-V compounds
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

A composite high reflectivity mirror (CHRM) with at least one relatively smooth interior surface interface. The CHRM includes a composite portion, for example dielectric and metal layers, on a base element. At least one of the internal surfaces is polished to achieve a smooth interface. The polish can be performed on the surface of the base element, on various layers of the composite portion, or both. The resulting smooth interface(s) reflect more of the incident light in an intended direction. The CHRMs may be integrated into light emitting diode (LED) devices to increase optical output efficiency.

Claims

1. A light emitting diode (LED), comprising:

a light emitting structure;

a current spreading layer on said light emitting structure comprising a smooth surface, wherein said current spreading layer smooth surface has a root mean square (RMS) roughness of not more than 1 nm;

a plurality of dielectric layers on said smooth surface of said current spreading layer opposite said light emitting structure, wherein an interface between two of said dielectric layers is smooth, said plurality of dielectric layers comprising first and second materials arranged in alternating layers on said current spreading layer, said second material comprising tantalum pentoxide (Ta2O5), wherein any layer of said first material closer to said current spreading layer is thicker than any layer of said first material farther from said current spreading layer and any layer of said second material closer to said current spreading layer is thicker than any layer of said second material farther from said current spreading layer; and

a reflective layer on one of said dielectric layers opposite said current spreading layer.

2. The LED of claim 1, said light emitting structure comprising an active region interposed between a p-type semiconductor layer and an n-type semiconductor layer.

3. The LED of claim 2, wherein said current spreading layer is on said p-type semiconductor layer opposite said active region.

4. The LED of claim 1, said light emitting structure comprising Group-III nitride materials.

5. The LED of claim 1, wherein said current spreading layer provides a reflectivity viewing angle cut-off above which said plurality of dielectric layers reflectivity is approximately 100%.

6. The LED of claim 5, wherein said plurality of dielectric layers provide improved reflectivity below said viewing angle cut-off compared to a similar LED without said at least one dielectric layer.

7. The LED of claim 1, wherein said first material comprises silicon dioxide (SiO₂).

8. The LED of claim 1, further comprising conductive vias through said at least one dielectric layer.

9. The LED of claim 1, said light emitting structure comprising:

at least two oppositely doped semiconductor layers;

an active region interposed between said at least two oppositely doped semiconductor layers; and

a substrate disposed such that said current spreading layer is on said substrate.

10. The LED of claim 1, said reflective layer comprising a metal.

11. The LED of claim 1, said reflective layer comprising a conductive material and electrically contacting said current spreading layer.

12. The LED of claim 1, said reflective layer comprising at least one conductive via through said at least one dielectric layer to said current spreading layer.