Granted Patent B2

US 8,716,038 · App. 12/715,820 · Granted May 6, 2014

Abstract

Claims (127)

1. A method for producing a light emitting diode (LED), comprising:

forming an LED on a substrate;

measuring a base emission characteristic of the formed LED;

developing a compensation scheme by selecting a group of candidate phosphors based on the base emission characteristic of the formed LED, wherein the group of the candidate phosphors is selected based on a distribution area in chromaticity plot;

selecting a plurality of phosphors, from the group of the candidate phosphors, based on the measured base emission characteristic of the formed LED such that a combined emission from the LED is closer to white light than the base emission characteristic; and

introducing the selected phosphors onto the LED.

2. The method of claim 1 wherein:

forming the LED on the substrate includes sequentially depositing an N-type GaN, InGaN, and P-type GaN onto a silicon substrate via epitaxial growth;

measuring the base emission characteristic of the formed LED includes measuring an emission wavelength of the LED with a peak intensity;

selecting the plurality of phosphors includes:

plotting the measured emission wavelength on a spectral locus of the chromaticity plot;

determining an emission point on a black body curve defined by the following:

I

⁡

(

v

,

T

)

⁢

dv

=

(

2

⁢

hv

3

c

2

)

⁢

1

ⅇ

hv

kT

-

1

⁢

dv

 where I(v,T)dv is an amount of energy emitted in the frequency range between v and v+dv by a black body at temperature T; h is the Planck constant; c is the speed of light in a vacuum; k is the Boltzmann constant; and v is the frequency of electromagnetic radiation;

the measured emission wavelength and the emission point of the black body define a straight line;

determining a phosphor wavelength as an intercept between the straight line and the spectral locus; and

selecting at least one of a composition, a concentration, and a quantity of the plurality of phosphors containing Cerium(III)-doped Yttrium Aluminum Garnet such that the selected phosphors collectively form an emission wavelength at least approximating the determined phosphor wavelength; and

introducing the selected phosphors includes introducing the selected phosphors onto the LED via inkjet printing.

3. The method of claim 1 wherein:

forming the LED on the substrate includes sequentially depositing an N-type GaN, InGaN, and P-type GaN onto a silicon substrate via epitaxial growth;

measuring the base emission characteristic of the formed LED includes measuring an emission wavelength of the LED with a peak intensity;

selecting the plurality of phosphors includes:

plotting the measured emission point of the LED on a spectral locus of the chromaticity plot;

determining an emission point on a black body curve defined by the following:

I

⁡

(

v

,

T

)

⁢

dv

=

(

2

⁢

hv

3

c

2

)

⁢

1

ⅇ

hv

kT

-

1

⁢

dv

 where I(v,T)dv is an amount of energy emitted in the frequency range between v and v+dv by a black body at temperature T; h is the Planck constant; c is the speed of light in a vacuum; k is the Boltzmann constant; and v is the frequency of electromagnetic radiation;

plotting first and second emission points of first and second phosphors on the chromaticity plot, wherein the first and second phosphors are chosen from the candidate phosphors;

the first and second emission points of the first and second phosphors and the emission point of the LED define a triangle;

selecting first and second wavelengths of the first and second phosphors such that the emission point on the black body curve lies inside the triangle; and

selecting a ratio of the first and second phosphors from the combinations of the candidate phosphors such that a combined emission from the LED and the phosphors at least approximates a white light; and

introducing the selected phosphors includes introducing the selected phosphors onto the LED via inkjet printing.

4. The method of claim 1 wherein:

forming the LED on the substrate includes sequentially depositing an N-type GaN, InGaN, and P-type GaN onto a silicon substrate via epitaxial growth;

measuring the base emission characteristic of the formed LED includes measuring at least one of an emission wavelength, an emission intensity, and an emission frequency;

selecting the plurality of phosphors includes selecting at least one of a composition, a concentration, and a quantity of the phosphors containing Cerium(III)-doped Yttrium Aluminum Garnet based on the measured emission characteristic of the formed LED and an operating temperature of the LED; and

introducing the selected phosphors includes introducing the selected phosphors onto the LED via inkjet printing.

5. The method of claim 1 wherein:

measuring the base emission characteristic of the formed LED includes measuring an emission wavelength of the LED with a peak intensity; and

selecting the plurality of phosphors includes empirically determining a ratio of at least two phosphors based on the combinations of the candidate phosphors stored in a database and the measured emission characteristic of the formed LED such that a combined emission from the LED and the phosphors at least approximates a white light.

6. The method of claim 1 wherein:

measuring the base emission characteristic of the formed LED includes measuring an emission wavelength of the LED with a peak intensity; and

selecting the plurality of phosphors includes selecting a combination of at least two phosphors from the combinations of the candidate phosphors stored in a database based on the measured emission characteristic of the formed LED such that a combined emission from the LED and the phosphors at least approximates a white light.

7. The method of claim 1 wherein:

the LED is one of a plurality of LEDs on the substrate; and

the method further includes for each of the LEDs:

measuring the base emission characteristic of the LED on the substrate;

selecting the plurality of phosphors based on the measured emission characteristic of the LED such that a combined emission from the LED and the phosphors at least approximates a white light; and

introducing the selected phosphors onto the LED.

8. The method of claim 1 wherein:

the LED is one of a plurality of LEDs on the substrate;

the method further includes for each of the LEDs:

measuring the base emission characteristic of the LED on the substrate;

selecting the plurality of phosphors based on the measured emission characteristic of the LED such that a combined emission from the LED and the phosphors at least approximates a white light; and

introducing the selected phosphors onto the LED;

inspecting emission characteristics of the plurality of LEDs with the introduced phosphors; and

repeating the measuring, selecting, and introducing operations until a variance in the emission characteristics of the plurality of LEDs is below a threshold.

9. A method of color correction of light emitting diodes (LEDs), comprising:

measuring a base emission characteristic of individual LEDs on a substrate;

developing an emission map of the LEDs on the substrate based on the measured base emission characteristics;

developing a compensation scheme by selecting a group of candidate phosphors based on the measured base emission characteristic, wherein the group of the candidate converter materials is selected at least based on a distribution area in a chromaticity plot;

selecting a plurality of converter materials from the group of the candidate converter materials based on the measured base emission characteristic;

for the individual LEDs, determining at least one of a composition and a concentration of the converter materials based on the emission map of the LEDs; and

introducing the selected converter materials onto the individual LEDs on the substrate.

10. The method of claim 9 wherein determining at least one of the composition and the concentration of the converter materials includes determining at least one of the composition and the concentration of the plurality of phosphors such that a combined emission from the individual LEDs and the phosphors at least approximates a white light.

11. The method of claim 9 wherein measuring the base emission characteristic of individual LEDs on the substrate includes measuring an emission wavelength of each of the LEDs on the substrate.

12. The method of claim 9 wherein measuring the base emission characteristic of individual LEDs on the substrate includes measuring an emission wavelength of the LEDs on the substrate.

13. The method of claim 9 wherein developing the emission map includes organizing the measured emission characteristic of the individual LEDs as individual records in accordance with the corresponding combinations of the candidate converter materials in the database.

14. The method of claim 9 wherein determining at least one of the composition and the concentration of the converter materials includes determining a ratio of a first phosphor and a second phosphor.

15. The method of claim 9 wherein determining at least one of the composition and the concentration of the converter materials includes looking up the database based on the emission map, the set of empirical information of the database containing empirical records indicating at least one of the composition and the concentration of the phosphors based on the corresponding emission characteristic in the emission map.

16. The method of claim 9 wherein:

measuring the base emission characteristic of individual LEDs includes measuring an emission wavelength of the individual LEDs with a peak intensity; and

determining at least one of the composition and the concentration of the converter material includes looking up a recipe database based on the emission wavelength with the peak intensity for the individual LEDs, the database containing records indicating at least one of the composition and the concentration of the phosphors based on the corresponding emission wavelength of the individual LEDs.

17. The method of claim 9 wherein:

measuring the base emission characteristic of individual LEDs includes measuring an emission wavelength of the individual LEDs with a peak intensity; and

determining at least one of the composition and the concentration of the converter materials includes looking up a recipe database based on the emission wavelength with the peak intensity for the individual LEDs, the database containing records indicating (1) at least one of a composition and a concentration of first and second phosphors based on the corresponding emission wavelength of the individual LEDs; and (2) a ratio of the first and second phosphors.

Assignments (8)