Light emitting diode structures
First Claim
1. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the first region comprises a p-doped semiconductor material and the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index.
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Abstract
According to one aspect of the present invention, a light emitting diode (LED) structure including an active core layer and at least one substrate layer having a first refractive index, comprises a 2-dimensional photonic quasicrystal in the structure, the photonic quasicrystal comprising an array of regions having a second refractive index, the array exhibiting long range order but short range disorder. The long range order is associated with diffractive properties of the structure and gives rise to uniform-far field diffraction patterns from the LED. The present invention enjoys the benefit of improved light extraction from LEDs without undesirable far field illumination patterns.
24 Citations
27 Claims
- 1. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the first region comprises a p-doped semiconductor material and the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index.
- 12. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the second layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index.
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17. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a periodically-repeated section of a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index.
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18. A light emitting diode (LED) structure comprising a first layer and a light-generating layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein light generated in the light-generating layer by spontaneous emission is extracted by the photonic quasicrystal and coupled out of the LED structure, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index, wherein the photonic quasicrystal is configured to have a bandgap that does not overlap with an emission spectrum of the light-generating layer.
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19. A light emitting diode (LED) structure comprising a first layer and a light-generating layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein light generated in the light-generating layer by spontaneous emission is extracted by the photonic quasicrystal and coupled out of the LED structure, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index, wherein the photonic quasicrystal is configured to have a bandgap that overlaps with an emission spectrum of the light-generating layer.
- 20. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the second layer disposed in a part of the LED structure closer to the lower surface of the first layer than the upper surface of the first layer, the second layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index, wherein the first region of the second layer comprises a metallic material.
- 22. A light emitting diode (LED) structure comprising a first layer and a light-generating layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein light generated in the light-generating layer by spontaneous emission is extracted by the photonic quasicrystal and coupled out of the LED structure, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index, wherein each sub-region comprises a material other than air.
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24. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, each sub-region having a refractive index different to the first refractive index, and wherein at least one parameter of the sub-regions varies across the array, the parameter selected from a group which includes a geometrical property and a material property of the sub-regions.
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25. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions exhibiting long range order but short range disorder, wherein the shape sub-regions have a substantially square cross-section in a plane parallel to the upper surface of the first layer.
- 26. A light emitting diode (LED) structure comprising a first layer, a second layer, and a light-generating layer disposed between the first and second layers, the first layer having an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer, wherein light generated in the light-generating layer by spontaneous emission emerges from the LED structure through the upper surface of the first layer, the first layer comprising a first region having a first refractive index and further comprising a 2-dimensional photonic quasicrystal, wherein the photonic quasicrystal comprises an array of sub-regions arranged in a pattern which exhibits long range order but short range disorder, each sub-region having a second refractive index different to the first refractive index, the pattern comprising either a Fibonacci spiral pattern or a Penrose tiling pattern or a square-triangle tiling pattern.
Specification