High efficiency light emitting diode (LED)

• US 7,956,371 B2
• Filed: 12/08/2006
• Issued: 06/07/2011
• Est. Priority Date: 12/08/2005
• Status: Expired due to Fees

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Speck, James S., DenBaars, Steven P., Nakamura, Shuji
• Primary Examiner(s): Pert; Evan
• Assistant Examiner(s): Rodela; Eduardo A
• Application Number:
  US11/608,439
• Publication Number:
  US 20070145397A1
• Time in Patent Office: 1,642 Days
• Field of Search: 257/98, 257/E33.072, 257/95, 257/10, 257/E33.006, 257/E33.056, 257/E33.061, 257/E33.064, 257/E33.065, 257/E33.067, 257/E33.068, 313/501, 313/502
• US Class Current: 257/98
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• 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
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

An (Al, Ga, In)N light emitting diode (LED), wherein light extraction from chip and/or phosphor conversion layer is optimized. By novel shaping of LED and package optics, a high efficiency light emitting diode is achieved.

Claims

1. An optical device, comprising:

a light emitting device comprised of at least an n-type layer having an n-type electrode, an active region, a p-type layer, and an n-type ZnO layer bonded to the p-type layer, wherein the n-type ZnO layer comprises at least one first shaped optical element for extracting light emitted by the active region, the first shaped optical element is shaped as a cone, a p-type electrode is placed on top of the cone, and the cone'"'"'s base is bonded to the p-type layer;

at least one second shaped optical element comprising a conical lens encapsulating both the light emitting device and the at least one first shaped optical element for extracting light emitted by the active region and the first shaped optical elements; and

a phosphor, optically coupled to the at least one second shaped optical element, wherein light in at least a first wavelength region emitted by the active region passes through the at least one second shaped optical elements and excites the phosphor to emit light in at least a second wavelength region.

2. The optical device of claim 1, wherein the at least one first optical element is wafer bonded to the light emitting device.

3. The optical device of claim 1, wherein at least one of the at least one first shaped optical elements comprises a ZnO optical element.

4. The optical device of claim 1, wherein at least one of the at least one first shaped optical elements is shaped to increase light extraction from the active region.

5. The optical device of claim 1, wherein the at least one first shaped optical elements include angles adjusted for light extraction efficiency from the active region.

6. The optical device of claim 1, wherein the at least one second shaped optical element is shaped for light extraction.

7. The optical device of claim 1, wherein the at least one second shaped optical element includes angles that are adjusted for light extraction efficiency.

8. The optical device of claim 1, wherein a layer that forms an interface between the active region and the at least one first shaped optical elements has a roughened surface.

9. The optical device of claim 1, further comprising an additional phosphor layer coupled to the phosphor layer.

10. The optical device of claim 1, further comprising a third shaped optical element encapsulating the active region, the at least one first shaped optical elements and the at least one second shaped optical elements for extracting light emitted by the active region, the first shaped optical elements, and the second shaped optical elements.

11. The optical device of claim 10, wherein the third shaped optical element comprises a reflector cup.

12. The optical device of claim 1, wherein the phosphor layer is shaped for light extraction efficiency.

13. The optical device of claim 1, wherein the light emitting device comprises at least one of the group consisting of:

(Al, Ga, In)N materials, (Al, Ga, In)As materials, (Al, Ga, In)P materials, compound semiconductor material from (Al, Ga, In)AsPNSb materials, and compound semiconductor material from ZnGeN₂ or ZnSnGeN₂ materials.

14. The optical device of claim 1, further comprising a reflective coating coupled to the at least one first optical element.

15. The optical device of claim 1, further comprising a reflector positioned between the phosphor layer and the active region which passes at least the first wavelength region and reflects at least a portion of light in the second wavelength region.

16. The optical device of claim 15, wherein the reflector is a distributed Bragg reflector.

17. A Light Emitting Diode (LED) assembly, comprising:

a substrate;

a light emitting device, comprising;

an n-type Group III nitride layer formed on the substrate;

an active layer, formed on the n-type Group III nitride layer, wherein the active layer emits light in at least a first wavelength region;

a p-type Group III nitride layer, formed on the active layer; and

at least one n-type oxide layer, bonded to the p-type Group-III nitride layer, for extracting light emitted by the active layer, the at least one n-type oxide layer being shaped into a cone that increases the efficiency of the light emitting device by reducing internal reflection of the light in the light emitting device, wherein a p-type electrode is placed on top of the cone, and the cone'"'"'s base is bonded to the p-type Group-III nitride layer;

an optical element, optically coupled to the at least one n-type oxide layer, for extracting light emitted by the active layer, the optical element being shaped into a conical lens and encapsulating both the light emitting device and the at least one n-type oxide layer; and

a phosphor, optically coupled to the at least one n-type oxide layer, wherein light in at least the first wavelength region emitted by the light emitting device passes through the phosphor and excites the phosphor to emit light in at least a second wavelength region.

18. The LED of claim 17, wherein the lens increases the efficiency of the LED by reducing light absorption in the LED.

19. The LED of claim 17, wherein the oxide layer is an electrode for the LED.

20. The LED of claim 19, further comprising a contact on top of the oxide layer.

21. The LED of claim 20, wherein the contact is p-type and the oxide layer is n-type.

22. The LED of claim 19, wherein the oxide layer is Zinc Oxide (ZnO), the cone is an etched cone, and the ZnO is wafer-bonded to the light emitting device comprising Group III nitride layers.

23. The LED of claim 22, wherein the phosphor is in a layer, a lower surface of the layer facing the LED is smooth and the phosphor is shaped on an outer surface of the layer.

24. A Light Emitting Diode (LED) emitting multiple wavelength regions of light, comprising:

an n-type Group III nitride layer;

an active Group III nitride layer formed on or above the n-type Group III nitride layer, wherein the active Group III nitride layer emits light in at least a first wavelength region;

a p-type Group III nitride layer formed on or above the active Group III nitride layer;

at least one n-type oxide layer, bonded to the p-type Group III nitride layer, for extracting light emitted by the active layer, wherein the at least one n-type oxide layer is substantially transparent in the first wavelength region, the at least one n-type oxide layer being shaped into a cone that increases the efficiency of the LED by reducing internal reflection of the light in the LED, a p-type electrode being placed on top of the cone, and the cone'"'"'s base being bonded to the p-type Group III nitride layer;

a conical lens, encapsulating both the active Group III nitride layer and the n-type oxide layer, wherein the lens increases the efficiency of the LED by reducing light absorption in the LED; and

a phosphor, optically coupled to the at least one n-type oxide layer such that light in at least the first wavelength region strikes the phosphor and excites the phosphor to emit light in at least a second wavelength region, such that light in at least the first wavelength region and the second wavelength region are emitted by the LED.