Light emitting system with high extraction efficency
First Claim
1. A solid state light emitting diode device comprising:
- an active layer emitting incoherent light in response to current injected into the layer;
a first structure comprising at least one waveguide layer adjacent to the active layer and two cladding layers wherein said active layer and said at least one waveguide layer are located between the two cladding layers, wherein an index of refraction of said at least one waveguide layer is higher than that of the cladding layers, said structure trapping the incoherent light generated by the active layer; and
a second structure comprising a photonic crystal structure adjacent to the first structure extracting the incoherent light that is trapped by the first structure and outputting incoherent light.
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Abstract
In an epitaxial structure of a solid state lighting system, electrical current injection into the active layer is used to excite the photon emission. The present invention employs a unique waveguide layer in the epitaxial structure for trapping the light generated by the active layer in the fundamental waveguide mode. Multiple photonic crystal regions located either outside or inside one or more current injection regions extract photons from the waveguide layer(s). This novel design optimizes the interplay of electrical pumping, radiation and optical extraction to increase the optical output to several times that of conventional LEDs. A transparent and conductive ITO layer is added to the surface of an epitaxial structure to reduce the interface reflection in addition to functioning as a current spreading layer. The present invention creates solid state lighting with high optical output and high power efficiency.
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Citations
29 Claims
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1. A solid state light emitting diode device comprising:
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an active layer emitting incoherent light in response to current injected into the layer; a first structure comprising at least one waveguide layer adjacent to the active layer and two cladding layers wherein said active layer and said at least one waveguide layer are located between the two cladding layers, wherein an index of refraction of said at least one waveguide layer is higher than that of the cladding layers, said structure trapping the incoherent light generated by the active layer; and a second structure comprising a photonic crystal structure adjacent to the first structure extracting the incoherent light that is trapped by the first structure and outputting incoherent light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A solid state light emitting device comprising:
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an active layer emitting light in response to current injected into the layer; a first structure adjacent to the active layer, said structure trapping the light generated by the active layer, said first structure comprising at least one waveguide layer adjacent to the active layer, said at least one waveguide layer and the active layer trapping the light generated by the active layer; a substrate layer; and a second structure adjacent to the first structure extracting the light that is trapped by the first structure, wherein the substrate layer has an electronic band gap that is wider than that of the active layer, so that light emitted by the active layer is not absorbed significantly by the substrate layer, and so that light emitted by the active layer is emitted from both sides of the device, wherein the second structure comprises holes that extend through the first structure and the active layer to a region between the substrate and the active layer, wherein the light extracted by the second structure and outputted from the device is incoherent.
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Specification