Claims
- 1. A light emitting diode comprising:
(a) a stacked structure having a top surface, a bottom surface, edges extending between said top and bottom surfaces and an emitting junction extending generally in a horizontal plane above the bottom surface, said emitting junction having an emission wavelength; said stacked structure having vertical directions normal to the emitting junction, and (b) a reflective diffraction grating disposed below said emitting junction on or in said stacked structure, said grating including a plurality of elements spaced apart from one another in a repeat direction, said grating being operative to diffract light at said emission wavelength directed vertically downwardly from said emission layer so that a substantial portion of such light is diffracted upwardly into the stacked structure in major diffraction directions oblique to the vertical and toward the edges of the structure.
- 2. A light emitting diode as claimed in claim 1 wherein said structure includes a substrate disposed between said junction and said grating, said substrate being transparent to light at said emission wavelength, said substrate defining portions of said edges.
- 3. A light emitting diode as claimed in claim 2 wherein said grating is arranged so that at least some of the upwardly-diffracted light passes through portions of said edges defined by said substrate.
- 4. A light emitting diode as claimed in claim 3 wherein said substrate has a thickness t in the vertical direction such that:
- 5. A light emitting diode as claimed in claim 1 wherein said grating is in the form of a plurality of elongated strips extending substantially parallel to one another, each said strip extending in a lengthwise direction perpendicular to said repeat direction, and wherein said stack structure has a dimension x in the lengthwise direction greater than said dimension w in the repeat direction.
- 6. A light emitting diode as claimed in claim 1 wherein said grating is a binary phase grating having alternating regions arranged to reflect light at phases differing by π.
- 7. A light emitting diode as claimed in claim 1 wherein said grating is disposed at the bottom of said substrate.
- 8. A light emitting diode as claimed in claim 7 wherein includes a set of first regions and second regions having different vertical elevations, such that said first regions project below said second region by a predetermined distance.
- 9. A light emitting diode as claimed in claim 1 wherein said stacked structure has a critical angle for total internal reflection at said edges of said stacked structure, and said major diffraction directions intercept the edges of the stacked structure at angles to the normal of the edge surface less than said critical angle.
- 10. A light emitting diode as claimed in claim 2 wherein said stack structure includes one or more nitride-based semiconductors defining said emitting junction.
- 11. A light emitting diode as claimed in claim 10 wherein said substrate consists essentially of sapphire.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of U.S. Provisional Patent Application Serial No. 60/332,288, filed Nov. 16, 2001, the disclosure of which is hereby incorporated by reference herein.
Provisional Applications (1)
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Number |
Date |
Country |
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60332288 |
Nov 2001 |
US |