LEDs with low optical loss electrode structures

• US 8,026,524 B2
• Filed: 09/22/2010
• Issued: 09/27/2011
• 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.
• Primary Examiner(s): Nguyen; Dao H
• Application Number:
  US12/888,360
• Publication Number:
  US 20110006332A1
• Time in Patent Office: 370 Days
• Field of Search: 257/79, 257/80, 257/82, 257/83, 257/84, 257/88, 257/98, 257/99, 257/103, 257/E21.158, 257/E27.121, 257/E33.005, 257/E33.069, 438/25, 438/29, 438/39, 438/42, 438/46, 372/38.09, 372/43.01, 372/50.124
• US Class Current: 257/79
• 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

Semiconductor devices in which one or more LEDs are formed include a dielectric region formed on a n/p region of the semiconductor, and that a metallic electrode can be formed on (at least partially on) the region of dielectric material. A transparent layer of a material such as Indium Tin Oxide can be used to make ohmic contact between the semiconductor and the metallic electrode, as the metallic electrode is separated from physical contact with the semiconductor by one or more of the dielectric material and the transparent ohmic contact layer (e.g., ITO layer). The dielectric material can enhance total internal reflection of light and reduce an amount of light that is absorbed by the metallic electrode.

Claims

1. A light emitting diode chip, comprising:

a semiconductor material capable of emitting light from a planar surface responsive to application of a potential across a first metallic wire bonding pad structure disposed on the planar surface and ohmicly coupled with an p-doped region of the semiconductor material, and a second metallic wire bonding pad structure ohmicly coupled with a n-doped region of the semiconductor material, and

wherein at least the first metallic bonding pad structure is ohmicly coupled with the p-doped region of the semiconductor material by a current spreading layer disposed on the planar surface that contacts both the first metallic bonding pad structure and the p-doped region of the semiconductor material, and wherein the first metallic bonding pad structure is separated physically from the semiconductor material by a non-perforated layer of dielectric material disposed on the p-doped region of the semiconductor material.

2. The light emitting diode chip of claim 1, wherein the first metallic wire bonding pad structure comprises a reflective layer facing the layer of dielectric material and the semiconductor material.

3. The light emitting diode chip of claim 1, wherein the layer of dielectric material is formed to have a thickness of at least one half of a wavelength of light emitted by the semiconductor material.

4. The light emitting diode chip of claim 1, wherein the layer of dielectric material is formed to have a thickness of at least one wavelength of light emitted by the semiconductor material.

5. The light emitting diode chip of claim 1, wherein the layer of dielectric material is formed to have a thickness of at least one and a half wavelengths of light emitted by the semiconductor material.

6. The light emitting diode chip of claim 1, wherein the layer of dielectric material is formed to have a thickness of at least one and three quarter wavelengths of light emitted by the semiconductor material.

7. The light emitting diode chip of claim 1, wherein the semiconductor material is supported by a transparent non-conductive substrate, and further comprising a cutout portion of the semiconductor material exposing a surface of the n-doped region, wherein the second metallic wire bonding pad structure ohmicly couples with the exposed surface of the n-doped region, and extends to the p-doped region, where the second metallic wire bonding pad structure is separated physically from the n-doped region by a second layer of dielectric material.

8. The light emitting diode chip of claim 7, wherein the substrate comprises sapphire.

9. A light emitting diode chip, comprising:

a semiconductor material in which is formed a diode junction, the diode junction capable of emitting light from a planar surface of the semiconductor material, responsive to application of a potential across a first metallic bond pad structure and a second metallic bond pad structure, wherein

one or more of the first metallic bond pad structure and the second metallic bond pad structure is separated from the semiconductor material by an optically transmissive non-perforated region of insulating material having an index of refraction greater than or equal to one and less than that of the semiconductor material and is supported from the planar surface, and

electrical continuity between one or more of the first metallic bond pad structure and the second metallic bond pad structure is provided by one or more optically transmissive conducting layers in ohmic contact with both the semiconductor material and respectively one or more of the first metallic bond pad structure and the second metallic bond pad structure.

10. The light emitting diode chip of claim 9, wherein the optically transmissive insulating material comprises porous silicon dioxide, and has a lower index of refraction than non-porous silicon dioxide.

11. The light emitting diode chip of claim 9, wherein the optically transmissive insulating material has a thickness of at least one half of a wavelength of light emitted by the LED device.

12. The light emitting diode chip of claim 9, wherein the insulating material has a thickness of about between ½

and 1¾

wavelengths of light emitted by the LED device in the optically transmissive insulating material.

13. The light emitting diode chip of claim 9, wherein the first metallic bond pad structure and the second metallic bond pad structure respectively comprise a layer of Rhenium disposed between the optically transmissive insulating material and a metallic bonding region comprising Au.

14. The light emitting diode chip of claim 9, wherein the optically transmissive dielectric material comprises porous Indium Tin Oxide.