Rare earth doped layer or substrate for light conversion

• US 20070120129A1
• Filed: 02/13/2006
• Published: 05/31/2007
• Est. Priority Date: 11/19/1999
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Keller, Bernd, Tarsa, Eric, Thibeault, Brian, Mack, Michael, DenBaars, Steven, Saxler, Adam
• Granted Patent: US 8,829,546 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 25/0756 Stacked arrangements of devices
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/343 characterised by the doping materials
• CPC Class Codes: H01L 33/465 with a resonant cavity structure
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01S 5/405 Two-dimensional arrays
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

A solid state light emitting device comprising an emitter structure having an active region of semiconductor material and a pair of oppositely doped layers of semiconductor material on opposite sides of the active region. The active region emits light at a predetermined wavelength in response to an electrical bias across the doped layers. An absorption layer of semiconductor material is included that is integral to said emitter structure and doped with at least one rare earth or transition element. The absorption layer absorbs at least some of the light emitted from the active region and re-emits at least one different wavelength of light. A substrate is included with the emitter structure and absorption layer disposed on the substrate.

Claims

1. A solid state light emitting device, comprising:

an emitter structure comprising;

an active region of semiconductor material;

a pair of oppositely doped layers of semiconductor material on opposite sides of said active region, said active region emitting light at a predetermined wavelength in response to an electrical bias across said doped layers; and

an absorption layer of semiconductor material integral to said emitter structure and doped with at least one rare earth or transition element, said absorption layer absorbing at least some of the light emitted from said active region and re-emitting at least one different wavelength of light.

2. The emitting device of claim 1, further comprising ohmic metals to contacts each of said oppositely doped layer to apply said bias across said doped layers.

3. The emitting device of claim 1, wherein said active region comprises multiple quantum wells, single quantum wells or double heterostructure.

4. The emitting device of claim 1, wherein said absorption layer is doped with at least one element from the group Er, Eu, Pr, Tm, Dy, Ce, Tb, Mn, Co and Cu.

5. The emitting device of claim 1, wherein said absorption layer is on said emitting structure with said emitting structure between said substrate and said absorbing layer.

6. The emitting device of claim 1 wherein said absorption layer is between said emitting structure and said substrate.

7. The emitting device of claim 1, wherein said absorption layer comprises a plurality of layer sections each of which is doped with one or more rare earth or transition elements in a different concentration or combination than the others of said layer sections.

8. The emitting device of claim 1, wherein said absorption layer comprises a plurality of layers of semiconductor materials, each of which is doped with one or more rare earth transition elements in a different combination or concentration than the others of said plurality of layers.

9. The emitting device of claim 1, comprising a light emitting diode (LED), said active layer emitting UV light and said absorption layer absorbing at least some of said UV light and re-emitting at least one different color of light.

10. The emitting device of claim 1, comprising a light emitting diode (LED), said active layer emitting blue light and said absorption layer absorbing at least some of said blue light and re-emitting at least one different color of light.

11. The emitting device of claim 1, wherein the light emitting from said device comprises the light emitting from an active region or the light re-emitting from said absorption layer or a combination thereof.

12. The light emitting device of claim 2, wherein one of said ohmic metals is on the top one of said oppositely doped layers, said one of said metals having a pattern with openings, said absorption layer arranged within said pattern openings.

13. The emitting device of claim 1, wherein said active region comprises a plurality of active layers emitting light at a predetermined wavelength in response to a bias, said absorption layer absorbing at least some of said light from at least one of said active layers and re-emits light at a different wavelength.

14. The emitting device of claim 13, wherein said active layers emit blue, green and UV light and said absorption layer absorbing said UV light and re-emitting a different wavelength of light, said LED emits blue, green, UV and said re-emitted light when all said active layers are emitting.

15. The emitting device of claim 1, wherein said active region emits one wavelength of light, said absorption layer doped throughout with more than one rare earth or transition element such that said absorption layer absorbs at least some of said active region light re-emits a wavelength combination of more than one wavelenth of light.

16. The emitting device of claim 7, wherein a bias can be selectively applied to said active region aligned with each of said layer sections causing one or more portions of said active region to emit light that will be primarily absorbed by its aligned one of said aligned layer sections and re-emitted as a different color.

17. The light emitting device of claim 16, further comprising ohmic metals on said oppositely doped layers to selectively apply said bias to said active layer above said color centers.

18. The emitting device of claim 1, comprising a solid state laser and further comprising mirrors on opposing surfaces, said light from said active region and said light absorbed and re-emitted by said absorption layer reflected between said mirrors to achieve stimulated emission.

19. The emitting device of claim 18, wherein said mirrors favor one or more colors for achieving stimulated emission.

20. The emitting device of claim 18, comprising a near UV laser with mirrors allowing substantially no near UV light to escape, said absorption layer within or at the edge of absorbing at the UV wavelength and re-emitting one or many colors spontaneously in the visible spectrum.

21. The emitting device of claim 1, further comprising electrical circuitry integrated with said device on a common substrate.

22. The emitting device of claim 1, further comprising a reflector to reflect one or both of said active region light or said re-emitted light, said reflector integral to said emitting device.

23. The emitting device of claim 21, wherein said reflector comprises a Distributed Bragg reflector.

24. The emitting device of claim 1, wherein said absorption layer is doped to give said absorption layer conductive characteristics.

25. The emitting device of claim 1, wherein said absorption layer comprises quantum dots.

26. A method for generating light from a solid state light emitting device, comprising:

exciting an optical emission from an active region within a first wavelength range;

illuminating an epitaxial semiconductor material with at least a portion of said optical emission, said epitaxial semiconductor material doped with a rare earth or transition element that absorbs light within said first wavelength range and provides stimulated re-emission within a different wavelength range; and

transmitting a wavelength combination of both emissions.

27. The method of claim 26, further comprising oppositely doped layers sandwiching said active region, wherein said exciting of optical emission from an active region comprises applying a bias across said oppositely doped layer.

28. The method of claim 26, wherein said epitaxial layer doped with rare earth or transition elements is arranged adjacent to one of said oppositely doped layers.

29. A light emitting device, comprising:

an active region of semiconductor material sandwiched by a p-type layer and an n-type layer, said active region emitting light at a wavelength in response to an electrical bias across said p-type and n-type doped layers;

a rare earth (RE) layer of semiconductor material doped with a rare earth or transition element, at least some of said light from said active region entering said RE layer wherein at least some of said entering light is absorbed by said rare earth or transition element, said absorbed light being re-emitted from rare earth or transition element at a wavelength different from said active region wavelength.

30. The LED of claim 29, emitting a wavelength combination of light from said active region and said rare earth or transition element.

31. The LED of claim 29, wherein said layers are made of a Group-III nitride material.

32. The LED of claim 29, wherein said RE layer is made of InAlGaN doped with a rare earth or transition element.

33. The LED of claim 32, wherein said RE layer comprises multiple quantum wells.