SEMICONDUCTOR COLOR-TUNABLE BROADBAND LIGHT SOURCES AND FULL-COLOR MICRODISPLAYS

• US 20100084668A1
• Filed: 10/02/2009
• Published: 04/08/2010
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Versitech Limited (Government of Hong Kong Special Administrative Region)
• Original Assignee: Versitech Limited (Government of Hong Kong Special Administrative Region)
• Inventors: WANG, Xianghua, HUI, Kwun Nam, CHOI, Hoi Wai
• Granted Patent: US 7,982,228 B2
• Time in Patent Office: Days
• US Class Current: 257/89
• CPC Class Codes: H01L 25/0756 Stacked arrangements of devices
• 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 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Methods and systems are provided that may be used to utilize and manufacture a light sources apparatus. A first light emitting diode emits light having a first wavelength, and a second light emitting diode for emitting light having a second wavelength. Each of the first and second light emitting diodes may comprise angled facets to reflect incident light in a direct toward a top end of the first light emitting diode. The second light emitting diode comprising angled facets may reflect incident light in a direction toward a top end of the second light emitting diode. A first distributed Bragg reflector is disposed between the top end of the first light emitting diode and a bottom end of the second light emitting diode to allow light from the first light emitting diode to pass through and to reflect light from the second light emitting diode.

Claims

1. A light sources apparatus, comprising:

a first light emitting diode for emitting light having a first wavelength, the first light emitting diode comprising angled facets to reflect incident light in a direction toward a top end of the first light emitting diode;

a second light emitting diode for emitting light having a second wavelength, the second light emitting diode being disposed above the top end of the first light emitting diode, and the second light emitting diode comprising angled facets to reflect incident light in a direction toward a top end of the second light emitting diode; and

a first distributed Bragg reflector disposed between the top end of the first light emitting diode and a bottom end of the second light emitting diode to allow light from the first light emitting diode to pass through and to reflect light from the second light emitting diode.

2. The light sources apparatus of claim 1, wherein at least one of the first light emitting diode and second light emitting diode is substantially monolithic.

3. The light sources apparatus of claim 1, wherein the first wavelength is longer than the second wavelength.

4. The light sources apparatus of claim 1, further comprising a third light emitting diode for emitting light having a third wavelength, the third light emitting diode being disposed above a top end of the second light emitting diode, and the third light emitting diode comprising angled facets to reflect incident light in a direct toward a top end of the third light emitting diode.

5. The light sources apparatus of claim 4, further comprising a second distributed Bragg reflector disposed between the top end of the second light emitting diode and a bottom end of the third light emitting diode to allow light from the second light emitting diode to pass through and to reflect light from the third light emitting diode.

6. The light sources apparatus of claim 4, wherein the first, second, and third light emitting diodes have a substantially identical design and emission area, the first, second, and third light emitting diodes being fabricated on different semiconductor materials with different bandgaps.

7. The light sources apparatus of claim 4, wherein light emitted from the first light emitting diode passes through the second and third light emitting diodes substantially without loss due to respective bandgaps.

8. The light sources apparatus of claim 4, wherein the first light emitting diode emits red light, the second light emitting diode emits green light, and the third light emitting diode emits blue light.

9. The light sources apparatus of claim 8, wherein the light sources apparatus emits red light in response to turning on only the first light emitting diode, green light in response to turning on only the second light emitting diode, and blue light in response to turning on only the third light emitting diode.

10. The light sources apparatus of claim 8, wherein the light sources apparatus simultaneously emits red light from the first light emitting diode, green light from the second light emitting diode, and blue light from the third light emitting diode, to generate polychromatic light.

11. The light sources apparatus of claim 10, wherein the polychromatic light comprises white light.

12. The light sources apparatus of claim 11, wherein the white light is produced without color conversion.

13. The light sources apparatus of claim 10, wherein an optical output of the light sources apparatus is tunable by varying intensity or amount of the red light, blue light, and green light.

14. The light sources apparatus of claim 4, further comprising a mirror coating on the angled facets of individual LEDs, the mirror coating comprising a layer of metal and adapted to reflect light and suppress leakage of light from the angled facets of the first, second, and third light emitting diode.

15. The light sources apparatus of claim 1, further comprising a layer of fluorescent microspheres on the second light emitting diode that emits light having a third wavelength when excited by light from the first light emitting diode or the second light emitting diode.

16. The light sources apparatus of claim 15, wherein the first light emitting diode emits red light, the second light emitting diode emits blue light, and the layer of fluorescent microspheres emits green light.

17. The light sources apparatus of claim 16, wherein the light sources apparatus simultaneously emits red light from the first light emitting diode and blue light from the second light emitting diode to generate polychromatic light through the layer of fluorescent microspheres.

18. An optoelectronic device comprising a stack of monochromatic microdisplays, the stack of monochromatic microdisplays comprising:

a first microdisplay to emit light having a first wavelength;

at least a second microdisplay to emit light having a second wavelength, the first wavelength being different from the second wavelength; and

a distributed Bragg reflector disposed between the first microdisplay and the at least a second microdisplay to allow light from the first microdisplay to pass through and to reflect light from the at least a second microdisplay.

19. The optoelectronic device of claim 18, wherein the first microdisplay and the at least the second microdisplay comprise a green microdisplay stacked on top of a red microdisplay and a blue microdisplay stacked on top of the green microdisplay.

20. The optoelectronic device of claim 19, wherein the green, blue, and red microdisplays have a substantially identical design and dimensions.

21. The optoelectronic device of claim 20, wherein the green, blue, and red microdisplays are fabricated on different semiconductor materials with bandgaps corresponding to the color being emitted.

22. The optoelectronic device of claim 19, wherein each individual monochromatic microdisplay comprises at least one pixel, the pixel comprising a two-dimensional array of matrix-addressable micro-meter scale light-emitting diodes.

23. The optoelectronic device according to claim 22, wherein an individual pixel on each of the red, green, and blue microdisplays is stacked on top of each other to form a pixel stack.

24. The optoelectronic device according to claim 23, wherein components in the pixel stack are individually controllable to achieve different emission intensities.

25. The optoelectronic device according to claim 23, wherein the emission from light emitting diodes in a pixel stack is optically mixed.

26. The optoelectronic device according to claim 23, wherein the pixel stack is arranged as a two-dimensional array of light emitting diode stacks, at least one of the light emitting diode stacks being color-tunable.

27. The optoelectronic device according to claim 18, wherein the second microdisplay is stacked on the first microdisplay, the optoelectronic device further comprising at least one layer of fluorescent microspheres on top of the second microdisplay.

28. The optoelectronic device according to claim 27, wherein the first microdisplay is a red microdisplay, the second microdisplay is a blue microdisplay, and the at least one layer of fluorescent microspheres comprises green fluorescent microspheres.

29. A wafer dicing process of electronic and optoelectronic devices based on laser micromachining to form diced chips with angled facets, the wafer dicing process comprising:

providing a processed wafer with multiple fabricated devices on an upper surface;

directing a laser beam at the wafer surface for wafer dicing;

reflecting the laser beam off a laser mirror, wherein the laser beam is incident onto the processed wafer at an oblique angle from a vertical axis, the incident beam forming a trench at a point of incidence by removal of semiconductor, metal or insulator materials;

translating the processed wafer so that the laser beam forms a trench around a periphery of devices on the processed wafer.

30. The wafer dicing process of claim 29, wherein the oblique angle ranges from about 0 degrees to about 89 degrees from the vertical axis.

31. The wafer dicing process of claim 29, wherein the processed wafer is ready for cleaving due to a presence of laser micromachined scribe lanes on the processed wafer.

32. The wafer dicing process of claim 29, further comprising removing the semiconductor, metal, or insulator materials from the processed wafer via at least one of:

ablation or absorption.