IP Library Granted Patent US 7,573,074
Granted Patent B2
US 7,573,074 · App. 11/437,570 · Granted Aug 11, 2009

LED electrode

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Quick Facts
Patent No.
US 7,573,074
App. No.
11/437,570
Granted
Aug 11, 2009
Kind
B2
Abstract

An electrode structure is disclosed for enhancing the brightness and/or efficiency of an LED. The electrode structure can have a metal electrode and an optically transmissive thick dielectric material formed intermediate the electrode and a light emitting semiconductor material. The electrode and the thick dielectric cooperate to reflect light from the semiconductor material back into the semiconductor so as to enhance the likelihood of the light ultimately being transmitted from the semiconductor material. Such LED can have enhanced utility and can be suitable for uses such as general illumination.

Claims (98)

1. An electrode structure for a semiconductor LED, the electrode structure comprising:

a metal electrode; and

an optically transmissive dielectric material having an index of refraction greater than or equal to one and less than that of a semiconductor upon which the dielectric material is formed and having a thickness greater than ½λ, the dielectric material being formed as a single layer to the electrode so as to enhance total internal reflection of light.

2. The electrode structure as recited in claim 1 , wherein:

a portion of the electrode is in electrical communication with a semiconducting material; and

another portion of electrode is deposed on top of the dielectric material.

3. The electrode structure as recited in claim 1 , wherein the dielectric material has a thickness of approximately 1.75λ.

4. The electrode structure as recited in claim 1 , wherein:

the electrode is formed upon a semiconductor material; and

the dielectric material is formed intermediate a portion of the electrode and the semiconductor material.

5. The electrode structure as recited in claim 1 , wherein:

the electrode is formed upon a semiconductor material;

the dielectric material is formed intermediate at least a portion of the electrode and the semiconductor material; and

the semiconductor material comprises at least one material selected from the group consisting of:

AlGaAs;

AlInGaP;

AlInGaN; and

GaAsP.

6. The electrode structure as recited in claim 1 , wherein the dielectric material comprises

at least one material selected from the group consisting of:

silicon dioxide;

silicon monoxide;

MgF 2 ;

siloxane polymers; and

air.

7. The electrode structure as recited in claim 1 , further comprising an ohmic contact layer formed between the electrode and a semiconductor.

8. The electrode structure as recited in claim 1 , further comprising:

an ohmic contact layer formed between the electrode and a semiconductor; and

wherein the ohmic contact layer comprises at least one material selected from the group consisting of:

indium tin oxide;

nickel oxide; and

RuO2.

9. The electrode structure as recited in claim 1 , further comprising:

an ohmic contact layer formed between the electrode and a semiconductor;

wherein the ohmic contact layer is part of the semiconductor device; and

wherein the ohmic contact layer comprises a heavily doped layer.

10. The electrode structure as recited in claim 1 , further comprising a current spreading layer formed between the metal and a semiconductor.

11. The electrode structure as recited in claim 1 , further comprising:

a current spreading layer formed between the metal and a semiconductor; and

wherein the current spreading layer comprises at least one material selected from the group consisting of:

indium tin oxide;

nickel; and

RuO2.

12. The electrode structure as recited in claim 1 , further comprising:

at least one pair of dielectric layers configured so as to define a DBR structure and disposed between the electrode and the dielectric; and

wherein each pair of dielectric layers is substantially optically transmissive, is comprised of layers of materials of different indices of refraction, and is a multiple of approximately ¼λ thick.

13. The electrode structure as recited in claim 1 , further comprising:

a dielectric base layer;

at least one pair of DBR dielectric layers formed between the electrode and the dielectric base layer, the dielectric base layer having a thickness greater than ½λ; and

wherein each DBR dielectric layer pair comprises at least one material selected from the group consisting of:

TiO2;

Ti3O5;

Ti2O3;

TiO;

ZrO2;

TiO2ZrO2Nb2O5;

CeO2;

ZnS;

A 12 O3;

SiN;

ITO;

niobium pentoxide (Nb2O5);

tantalum pentoxide (Ta2O5); and

siloxane polymers SiO, SiO2, or MgF2.

14. The electrode structure as recited in claim 1 , wherein the electrode comprises at least one metal layer.

15. The electrode structure as recited in claim 1 , wherein;

the electrode comprises at least one metal layer; and

wherein the metal layer(s) are selected from the group consisting of:

Al;

Ag;

Rh;

Pd;

Cu;

Au;

Cr;

platinum;

titanium;

nickel/gold alloys;

chrome/gold alloys;

silver/aluminum mixtures; and

combinations thereof.

16. The electrode structure as recited in claim 1 , wherein the electrode is formed upon a semiconductor material so as to define a lateral structure.

17. The electrode structure as recited in claim 1 , wherein the electrode is formed upon a semiconductor material so as to define a vertical structure.

18. The electrode structure as recited in claim 1 , wherein a portion of the metal forms an area for wire bonding.

19. The electrode structure as recited in claim 1 , wherein a portion of the metal makes an electrical contact to a semiconductor material at the edges of a dielectric material.

20. The electrode structure as recited in claim 1 , wherein a portion of the metal makes an electrical contact to the semiconductor material through openings in the dielectric material.

21. The electrode structure as recited in claim 1 , wherein the dielectric material is porous.

22. The electrode structure as recited in claim 1 , wherein the dielectric material comprises porous ITO.

23. The electrode structure as recited in claim 1 , wherein the dielectric material is porous SiO 2 .

24. The electrode structure as recited in claim 1 , wherein the dielectric material is porous enough to reduce its effective index of refraction such that total internal reflection occurs within the semiconductor material.

25. A reflective electrode structure comprising:

a metal electrode;

an AlInGaN material configured to emit light about a central wavelength λ;

silicon dioxide dielectric material formed upon the AlInGaN material, the dielectric material having a thickness greater than ½ λ so as to enhance total internal reflection of light; and

wherein a portion of the electrode is formed over the dielectric material and another portion of the electrode is in ohmic contact with a semiconductor material.

26. The reflective electrode structure as recited in claim 25 , wherein the dielectric material and electrode make physical contact to the semiconductor via an ITO layer.

27. A method for forming an electrode structure for an LED, the method comprising forming a dielectric material as a single layer having a thickness greater than ½λ upon a semiconductor material and forming a conductive electrode such that the dielectric material electrically isolates at least one portion of the electrode from the semiconductor material while allowing at least one other portion of the electrode to make electrical contact with the semiconductor material, wherein the portion(s) of the electrode that the dielectric material electrically isolates from the semiconductor material and the portion(s) of the electrode that make contact with the semiconductor material are formed of the same material.

28. The method as recited in claim 27 wherein the portion(s) of the electrode that the dielectric material electrically isolates from the semiconductor material and the portion(s) of the electrode that make contact with the semiconductor material are formed as a single layer.

Assignments (2)
TERMINATION AND RELEASE OF SECURITY INTEREST IN PATENT COLLATERAL RECORDED AT REEL/FRAME 029281/0844 ON NOVEMBER 12, 2012 Recorded Nov 4, 2013
From: WELLS FARGO BANK, NATIONAL ASSOCIATION (SUCCESSOR BY ASSIGNMENT FROM WHITE OAK GLOBAL ADVISORS, LLC, AS COLLATERAL AGENT)
To: BRIDGELUX, INC.
Reel/Frame 031560/0102 →
SECURITY AGREEMENT Recorded Nov 12, 2012
From: BRIDGELUX, INC.
To: WHITE OAK GLOBAL ADVISORS, LLC, AS COLLATERAL AGENT
Reel/Frame 029281/0844 →