Droop-free high output light emitting devices and methods of fabricating and operating same

• US 7,843,060 B2
• Filed: 08/27/2008
• Issued: 11/30/2010
• Est. Priority Date: 06/11/2007
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John Adam
• Primary Examiner(s): Garber; Charles D
• Assistant Examiner(s): STEVENSON, ANDRE C
• Application Number:
  US12/199,592
• Publication Number:
  US 20090050924A1
• Time in Patent Office: 825 Days
• Field of Search: None
• US Class Current: 257/724
• 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 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

Light emitting devices include a semiconductor light emitting diode that is configured to operate at a substantially droop-free quantum efficiency while producing warm white light output of at least about 100 lumens/cool white light output of at least about 130 lumens. The semiconductor light emitting diode may include a single semiconductor die of at least about 4 mm² in area that operates at a current density of less than about 9 A/cm², so as to operate at the substantially droop-free quantum efficiency. Related fabricating and operating methods are also disclosed.

Claims

1. A light emitting device comprising:

a semiconductor light emitting diode comprising a single semiconductor die that is configured to operate at a substantially droop-free quantum efficiency that has less than about 5% deviation from linearity of quantum efficiency while producing warm white light output of at least about 100 lumens/cool white light output of at least about 130 lumens.

2. A light emitting device according to claim 1 wherein the single semiconductor die is of at least about 4 mm² in area and operates at a current density of less than about 9 A/cm² so as to operate at the substantially droop-free quantum efficiency.

3. A light emitting device according to claim 2 wherein the single semiconductor die is configured to operate at an input voltage of about 3V and an input current of about 350 mA.

4. A light emitting device according to claim 2 wherein the single semiconductor die is a single square semiconductor die that includes four sides, each of which includes a midpoint and which define four corners, the light emitting device further comprising a plurality of bond pads, a respective one of which is located at a respective midpoint and at a respective corner of the single square semiconductor die.

5. A light emitting device according to claim 4 further comprising at least five spaced apart cathode contact lines on the single semiconductor die extending parallel to a first opposing pair of the four sides and at least five spaced apart cathode contact lines on the single semiconductor die extending parallel to a second opposing pair of the four sides, and electrically connected to the bond pads.

6. A light emitting device according to claim 4 further comprising a plurality of wire bond connections that are electrically connected to a subset, less than all, of the plurality of bond pads.

7. A light emitting device according to claim 2 further comprising at least five bond pads on the single square semiconductor die.

8. A method of fabricating a light emitting device that can produce at least about 100 lumens of warm white light/at least about 130 lumens of cool white light comprising:

increasing a die size of a semiconductor light emitting diode die to at least about 4 mm² and reducing operating current density in the semiconductor light emitting diode die to less than about 9 A/cm² to operate the semiconductor light emitting diode die at a substantially droop-free quantum efficiency that has less than about 5% deviation from linearity of quantum efficiency.

9. A method according to claim 8 wherein the semiconductor light emitting diode die is configured to operate at an input voltage of about 3V and an input current of about 350 mA.

10. A method according to claim 8 wherein the semiconductor light emitting diode die comprises a single square semiconductor die that includes four sides, each of which includes a midpoint and which define four corners, the method further comprising fabricating a plurality of bond pads on the single square semiconductor die, a respective one of which is located at a respective midpoint and at a respective corner of the single square semiconductor die.

11. A method according to claim 10 further comprising fabricating at least five spaced apart cathode contact lines on the single semiconductor die extending parallel to a first opposing pair of the four sides and at least five spaced apart cathode contact lines on the single semiconductor die extending parallel to a second opposing pair of the four sides, and electrically connected to the bond pads.

12. A method according to claim 10 further comprising connecting a plurality of wire bonds to a subset, less than all, of the plurality of bond pads.

13. A method of operating a light emitting device to produce at least about 100 lumens of warm white light/at least about 130 lumens of cool white light comprising:

reducing operating current density in a semiconductor light emitting diode die having a die size of at least about 4 mm² to less than about 9 A/cm² so as to operate the semiconductor light emitting diode die at a substantially droop-free quantum efficiency that has less than about 5% deviation from linearity of quantum efficiency.

14. A method according to claim 13 wherein the semiconductor light emitting diode die is configured to operate at an input voltage of about 3V and an input current of about 350 mA.