LOW OPTICAL LOSS ELECTRODE STRUCTURES FOR LEDS

• US 20110024782A1
• Filed: 09/22/2010
• Published: 02/03/2011
• Est. Priority Date: 05/19/2006
• Status: Active Grant

• Current Assignee: Bridgelux Incorporated
• Original Assignee: Bridgelux Incorporated
• Inventors: Lester, Steven D., So, William W., Shum, Frank T.
• Granted Patent: US 8,115,226 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/385 the electrode extending at least partially onto a side surface of the semiconductor body
• 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 33/42 Transparent materials
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• 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

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 dielectric material formed intermediate the electrode and a light emitting semiconductor material. Electrical continuity between the semiconductor material and the metal electrode is provided by an optically transmissive ohmic contact layer, such as a layer of Indium Tin Oxide. The metal electrode thus can be physically separated from the semiconductor material by one or more of the dielectric material and the ohmic contact layer. The dielectric layer can increase total internal reflection of light at the interface between the semiconductor and the dielectric layer, which can reduce absorption of light by the electrode. Such LED can have enhanced utility and can be suitable for uses such as general illumination.

Claims

1. An electrode structure for interfacing with a semiconductor material of a Light Emitting Diode (LED), the electrode structure comprising:

a metal electrode;

a dielectric material disposed between at least a portion of the metal electrode and a surface of the semiconductor material, the 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

an optically transmissive ohmic contact layer establishing ohmic contact between the metal electrode and the semiconductor material, wherein the metal electrode is physically separated from the surface of the semiconductor material by one or more of the optically transmissive ohmic contact layer and the dielectric material.

2. The electrode structure of claim 1, wherein, the optically transmissive ohmic contact layer comprises at least one material selected from the group consisting of:

Indium Tin Oxide, Nickel Oxide, and RuO₂.

3. The electrode structure of claim 1, wherein the metal electrode comprises a bond pad, and the optically transmissive dielectric material is disposed between the bond pad and the semiconductor material.

4. The electrode structure of claim 1, wherein the metal electrode comprises a reflective layer facing the surface of the semiconductor material.

5. The electrode structure of claim 1, wherein the optically transmissive dielectric material comprises porous silicon dioxide, and has a lower index of refraction than non-porous silicon dioxide.

6. The electrode structure of claim 1, wherein the optically transmissive dielectric material has a thickness of at least one half of a wavelength of light emitted by the LED device.

7. The electrode structure of claim 1, wherein the optically transmissive dielectric material has a thickness of about between ½

and 1¾

wavelengths of light emitted by the LED device in the dielectric material.

8. The electrode structure of claim 1, wherein the metal electrode comprises a layer of Rhenium disposed between the optically transmissive dielectric material and metallic bonding region comprising Au.

9. The electrode structure of claim 1, wherein the optically transmissive dielectric material comprises porous Indium Tin Oxide.

10. An electrode structure for interfacing with a semiconductor material of a Light Emitting Diode (LED) device, the electrode structure comprising:

a metal electrode;

a dielectric material disposed between the metal electrode and a surface of the semiconductor material, the dielectric material having an index of refraction greater than or equal to one and less than that of the semiconductor material, the dielectric material covering only a portion of the surface of the semiconductor material; and

a optically transmissive ohmic contact layer contacting the electrode and the surface of the semiconductor in an area of the surface of the semiconductor material not covered by the optically transmissive dielectric material.

11. The electrode structure of claim 10, wherein the dielectric material has a thickness of at least one half of a wavelength of light emitted by the LED device.

12. The electrode structure of claim 10, wherein the optically transmissive ohmic contact layer comprises Indium Tin Oxide.

13. The electrode structure of claim 10, wherein the optically transmissive ohmic contact layer is disposed between the surface of the semiconductor material, and the metal electrode.