Apparatus for performing wavelength-conversion using phosphors with light emitting diodes

• US 6,366,018 B1
• Filed: 10/20/1999
• Issued: 04/02/2002
• Est. Priority Date: 10/21/1998
• Status: Expired due to Term

• Current Assignee: Emcore Corporation, Lightscape Materials, Inc.
• Original Assignee: Emcore Corporation, Sarnoff Corporation (SRI International, Inc.)
• Inventors: Ferguson, Ian Thomas, Karlicek, Robert Frank Jr., Connolly, John Charles, Garbuzov, Dmitri Zalmanovich
• Primary Examiner(s): BERCK, KENNETH A
• Application Number:
  US09/420,905
• Time in Patent Office: 895 Days
• Field of Search: 313/112, 313/113, 313/114, 313/502, 313/506, 313/542, 362/293, 362/800, 362/260, 257/98, 257/97, 257/13
• US Class Current: 313/542
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/50 Wavelength conversion elements

Abstract

An apparatus, comprises an active region, a phosphor layer and a reflective layer. The active region is configured to emit light having a first band of wavelengths from a first group of wavelengths. The phosphor layer is disposed between and in contact with the active region and an exterior medium. The phosphor layer is configured to convert the first band of wavelengths of light emitted from the active region to a second band of wavelengths. A center wavelength of the second band of wavelengths is greater than a center wavelength of the first band of wavelengths. The reflective layer is optically coupled to the active region. The active region is disposed between the reflective layer and the phosphor layer. The reflective layer is configured to reflect at least the first band of wavelengths and the second band of wavelengths.

Claims

1. An apparatus, comprising:

a substrate;

an active region coupled to said substrate and including a plurality of device layers and an active layer, said active region configured to emit light having a first band of wavelengths from a first group of wavelengths;

a phosphor layer being disposed between said active region and an exterior medium, said phosphor layer being configured to convert the first band of wavelengths of light emitted from said active region to a second band of wavelengths, a center wavelength of the second band of wavelengths being greater than a center wavelength of the first band of wavelengths; and

a reflective layer being optically coupled to said active region, said active region being disposed between said reflective layer and said phosphor layer, said reflective layer being configured to reflect at least the first band of wavelengths and the second band of wavelengths;

wherein, at least one of said device layers, active layer and substrate includes a first side, second side and at least one sidewall inclined from said second side at an angle, each said at least one layer has its own first refraction index, the sidewall of the at least one layer is adjacent to and in contact with said exterior medium having a second refractive index, and the angle, for each layer from the at least one layer, is not greater than ninety degrees minus arcsin of the second refractive index divided by the first refractive index of that layer.

2. The apparatus of claim 1, wherein:

said plurality of device layers includes a first device layer and a second device layer, and

the first device layer is between and in contact with said reflective layer and the active layer of said active region.

3. The apparatus of claim 2, further comprising;

a second reflective layer disposed between and in contact with said substrate and said phosphor layer, said second reflective layer being configured to transmit light having the first band of wavelengths transmitted from said active region and reflect light having the second band of wavelengths transmitted from said phosphor layer;

wherein, said substrate is disposed between said phosphor layer and the second device layer of the active region.

4. The apparatus of claim 1, wherein, the reflective layer is between and in contact with said substrate and at least one of said device layers of said active region.

5. The apparatus of claim 4, further comprising:

a second active region, said second active region configured to emit light having the first band of wavelengths;

a second phosphor layer being disposed between said second active region and the exterior medium, said second phosphor layer being configured to convert the first band of wavelengths of light emitted from said second active region to a third band of wavelengths, a center wavelength of the third band of wavelengths being greater than the center wavelength of the first band of wavelengths; and

a third active region, said third active region having an active layer, a first device layer and a second device layer, the second device layer of said third active region being disposed adjacent to said reflective layer, said third active region configured to emit light having the first band of wavelengths,

wherein, said reflective layer is further optically coupled to said second active region and said third active region, said second active region is disposed between said reflective layer and said second phosphor layer, and said reflective layer is configured to reflect the third band of wavelengths.

6. The apparatus of claim 5, further comprising:

a third phosphor layer being disposed between said third active region and the exterior medium, said third phosphor layer being configured to convert the first band of wavelengths of light emitted from said third active region to a fourth band of wavelengths, a center wavelength of the fourth band of wavelengths being greater than the center wavelength of the first band of wavelengths.

7. The apparatus of claim 1, wherein the first group of wavelengths are between approximately 300 nm and approximately 500 nm.

8. The apparatus of claim 1, wherein:

the first group of wavelengths are producible by the active layer constructed of at least Al_xGa_1-xN, x is a value between zero and one.

9. The apparatus of claim 7, wherein:

the center wavelength of the first band of wavelengths is between approximately 400 nm and approximately 550 nm;

the center wavelength of the second band of wavelengths is between approximately 430 nm and 650 nm; and

the center wavelength of the third band of wavelengths is between approximately 550 nm and 750 nm.

27. The apparatus of claim 1, wherein the phosphor layer is in contact with said active region and an exterior medium.

10. An apparatus, comprising:

an active region having an active layer, a first device layer and a second device layer, said active region configured to emit light having a first band of wavelengths from a first group of wavelengths;

a phosphor layer, said phosphor layer being configured to convert the first band of wavelengths of light emitted from said active region to a second band of wavelengths, a center wavelength of the second band of wavelengths being greater than a center wavelength of the first band of wavelengths; and

a substrate disposed between and in contact with the first device layer of said active region and said phosphor layer,

wherein, at least one layer from the group of the first device layer, the active layer, the second device layer and said substrate each has a first side, a second side and a side wall between the first side and the second side, the first side having a first area, the second side having a second area greater than the first area; and

,

wherein, each layer from the at least one layer has its own first refraction index, the sidewall of the at least one layer is adjacent to and in contact with an exterior medium having a second refractive index, and the at least one side wall is inclined from the second side of the at least one layer at an angle not greater than ninety degrees minus arcsin of the second refractive index divided by the first refractive index of that layer.

11. The apparatus of claim 10, wherein:

the angle for the at least one side wall is substantially between approximately forty degrees and approximately sixty degrees.

12. The apparatus of claim 10, wherein:

the first device layer of said active region has its own side wall having its own angle,

the active layer of said active region has its own side wall having its own angle, and

the second device layer of said active region has its own side wall having its own angle.

13. The apparatus of claim 10, wherein the first group of wavelengths are between approximately 300 nm and approximately 500 nm.

14. The apparatus of claim 10, wherein:

the first group of wavelengths are producible by the active layer constructed of at least Al_xGa_1-xN, x is a value between zero and one.

15. The apparatus of claim 10, wherein:

the active layer is constructed of at least InGaN/Al_xGa_1-xN, x is a value between zero and one,

the first device layer is a p-type GaN layer, and

the second device layer is an n-type GaN layer.

16. An apparatus, comprising:

an active region having an active layer, a first device layer and a second device layer, the active layer of said active region being configured to emit light having a first band of wavelengths from a first group of wavelengths; and

,

a phosphor layer, the first device layer of said active region being disposed between said phosphor layer and the active layer of said active region, said phosphor layer being configured to convert the first band of wavelengths of light emitted from said active region to a second band of wavelengths, a center wavelength of the second band of wavelengths being greater than a center wavelength of the first band wavelengths;

wherein,

the first device layer has a first side, a second side and a side wall between the first side and the second side, the first side having a first area and being adjacent to the active layer of said active region, the second side having a second area greater than the first area and being adjacent to said phosphor layer,

the side wall is inclined from the second side of the first device layer at an angle being less than ninety degrees; and

,

the substrate has a first refraction index, the sidewall of said substrate is adjacent to an exterior medium having a second refractive index, and the angle is less than about ninety degrees minus arcsin of the second refractive index divided by the first refractive index.

17. The apparatus of claim 16, wherein:

the angle is substantially between approximately forty degrees and approximately sixty degrees.

18. The apparatus of claim 16, wherein:

the active layer of said active region has a side wall having the angle of the side wall of the first device layer, and

the second device layer of said active region has a side wall having the angle of the side wall of the first device layer.

19. The apparatus of claim 16, wherein the first group of wavelengths are between approximately 300 nm and approximately 500 nm.

20. The apparatus of claim 16, wherein:

the first group of wavelengths are producible by the active layer constructed of at least Al_xGa_1-xN, x is a value between zero and one.

21. The apparatus of claim 16 further comprising:

a second active region including a second active layer, a third device layer and a fourth device layer, the second active layer of said second active region being configured to emit light having the first band of wavelengths; and

,

a second phosphor layer, the third device layer of said active region being disposed between said second phosphor layer and said second active layer, said second phosphor layer being configured to convert the first band of wavelengths of light emitted from said second active region to a third band of wavelengths, a center wavelength of the third band of wavelengths being greater than a center wavelength of the first band of wavelengths;

wherein,

the third device layer has a first side having a first area and being adjacent to the second active layer of said second active region, a second side having a second area greater than the first area of the third device layer and being adjacent to said second phosphor layer, and a side wall between the first side and the second side of the third device layer; and

,

the side wall of the third device layer is formed at a second angle inclined from the second side of the third device layer by less than ninety degrees.

22. The apparatus of claim 21, wherein:

the second angle is substantially between approximately forty degrees and approximately sixty degrees.

23. The apparatus of claim 21, wherein:

the active layer of said second active region has a side wall having the second angle of the side wall of the third device layer, and

the fourth device layer of said second active region has a side wall having the second angle of the side wall of the third device layer.

24. The apparatus of claim 21, further comprising:

a third active region including a third active layer, a fifth device layer and a sixth device layer, the third active layer of said third active region being configured to emit light having the first band of wavelengths.

25. The apparatus of claim 24, wherein:

the fifth device layer has a first side, a second side and a side wall between the first side and the second side of the fifth device layer, the first side of the fifth device layer having a first area and being adjacent to the third active layer of said third active region, the second side of the fifth device layer having a second area greater than the first area of the fifth device layer,

the side wall of the third device layer is formed at a third angle inclined from the second side of the fifth device layer, the second angle being less than ninety degrees,

the third active layer of said third active region has a side wall having the third angle of the side wall of the fifth device layer, and

the sixth device layer of said third active region has a side wall having the third angle of the side wall of the fifth device layer.

26. The apparatus of claim 23, wherein:

the center wavelength of the first band of wavelengths is between approximately 400 nm and approximately 550 nm;

the center wavelength of the second band of wavelengths is between approximately 430 nm and 650 nm; and

the center wavelength of the third band of wavelengths is between approximately 550 nm and 750 nm.