PHOTONIC STRUCTURES FOR EFFICIENT LIGHT EXTRACTION AND CONVERSION IN MULTI-COLOR LIGHT EMITTING DEVICES

• US 20100327305A1
• Filed: 07/28/2010
• Published: 12/30/2010
• Est. Priority Date: 10/14/2005
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: David, Aurélien J.F., Petroff, Pierre M., Diana, Frédéric S., Weisbuch, Claude C.A.
• Granted Patent: US 8,227,825 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/1213 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/502 Wavelength conversion materials

Abstract

A high efficiency light emitting diode (LED) comprised of a substrate, a buffer layer grown on the substrate (if such a layer is needed), a first active region comprising primary emitting species (PES) that are electrically-injected, a second active region comprising secondary emitting species (SES) that are optically-pumped by the light emitted from the PES, and photonic crystals, wherein the photonic crystals act as diffraction gratings to provide high light extraction efficiency, to provide efficient excitation of the SES, and/or to modulate the far-field emission pattern.

Claims

1. A high efficiency light emitting diode (LED) comprising:

(a) a first active region including one or more primary emitting species (PES) for emitting light at a first wavelength, wherein the PES emit the light at the first wavelength when electrically-injected;

(b) a second active region including one or more secondary emitting species (SES) for emitting light at a second wavelength, wherein the SES emit the light at the second wavelength when optically-pumped by the light emitted by the PES at the first wavelength; and

(c) one or more photonic crystals, formed proximate to the first and second regions, wherein the photonic crystals are chosen to extract total internal reflection (TIR) or waveguided (WG) modes of the light emitted by the PES or the SES.

2. The LED of claim 1, wherein different ones of the SES are positioned on different regions of the LED to form multi-color pixels.

3. The LED of claim 2, wherein each type of pixel in the multi-color pixels has a different photonic crystal to obtain homogeneous efficiency and directionality for all colors.

4. The LED of claim 1, wherein the SES is positioned relative to a low refraction index layer to prevent coupling of the SES'"'"'s evanescent waves to the TIR or WG modes of the light emitted by the PES or the SES.

5. The LED of claim 1, wherein the photonic crystals increase excitation of the SES by the light emitted by the PES at the first wavelength.

6. The LED of claim 1, wherein the photonic crystals are one-dimensional (1D) gratings that diffract differently different components of the light emitted by the PES or the SES.

7. The LED of claim 1, wherein the photonic crystals are one-dimensional (1D) gratings having a periodicity, such that the TIR or WG modes of the light emitted by the PES or the SES are diffracted at angles nearly parallel to the LED'"'"'s layers, so that the diffracted light propagates nearly in-plane in the SES'"'"' layer.

8. The LED of claim 1, wherein the photonic crystals are one-dimensional (1D) gratings integrated at different positions on the LED with different orientations to diffract the light emitted by the PES or the SES in more than one direction.

9. The LED of claim 1, wherein the photonic crystals are two-dimensional (2D) gratings that improve extraction of the light emitted by the PES or the SES in more than one direction.

10. The LED of claim 1, wherein the photonic crystals are fabricated on separate membranes and then are positioned on the LED.

11. The LED of claim 1, further comprising means for confining or thinning one or more layers containing the TIR or WG modes, in order to increase the TIR or WG modes'"'"' overlap with the photonic crystals.

12. A method of fabricating a high efficiency light emitting diode (LED), comprising:

(a) forming a first active region including one or more primary emitting species (PES) for emitting light at a first wavelength, wherein the PES emit the light at the first wavelength when electrically-injected;

(b) forming a second active region including one or more secondary emitting species (SES) for emitting light at a second wavelength, wherein the SES emit the light at the second wavelength when optically-pumped by the light emitted by the PES at the first wavelength; and

(c) forming one or more photonic crystals, proximate to the first and second regions, wherein the photonic crystals are chosen to extract total internal reflection (TIR) or waveguided (WG) modes of the light emitted by the PES or the SES.

13. The method of claim 12, wherein different ones of the SES are positioned on different regions of the LED to form multi-color pixels.

14. The method of claim 13, wherein each type of pixel in the multi-color pixels has a different photonic crystal to obtain homogeneous efficiency and directionality for all colors.

15. The method of claim 12, wherein the SES is positioned relative to a low refraction index layer to prevent coupling of the SES'"'"'s evanescent waves to the TIR or WG modes of the light emitted by the PES or the SES.

16. The method of claim 12, wherein the photonic crystals increase excitation of the SES by the light emitted by the PES at the first wavelength.

17. The method of claim 12, wherein the photonic crystals are one-dimensional (1D) gratings that diffract differently different components of the light emitted by the PES or the SES.

18. The method of claim 12, wherein the photonic crystals are one-dimensional (1D) gratings having a periodicity, such that the TIR or WG modes of the light emitted by the PES or the SES are diffracted at angles nearly parallel to the LED'"'"'s layers, so that the diffracted light propagates nearly in-plane in the SES'"'"' layer.

19. The method of claim 12, wherein the photonic crystals are one-dimensional (1D) gratings integrated at different positions on the LED with different orientations to diffract the light emitted by the PES or the SES in more than one direction.

20. The method of claim 12, wherein the photonic crystals are two-dimensional (2D) gratings that improve extraction of the light emitted by the PES or the SES in more than one direction.

21. The method of claim 12, wherein the photonic crystals are fabricated on separate membranes and then are positioned on the LED.

22. The method of claim 12, further comprising confining or thinning one or more layers containing the TIR or WG modes, in order to increase the TIR or WG modes'"'"' overlap with the photonic crystals.

23. A device fabricated according to the method of claim 12.