Nano-photonics reflector for LED emitters
A system, method and device for use as a reflector for a light emitting diode (LED) are disclosed. The system, method and device include a first layer designed to reflect transverse-electric (TE) radiation emitted by the LED, a second layer designed to block transverse-magnetic (TM) radiation emitted from the LED, and a plurality of ITO layers designed to operate as a transparent conducting oxide layer. The first layer may be a one-dimension (1D) distributed Bragg reflective (DBR) layer. The second layer may be a two-dimension (2D) photonic crystal (PhC), a three-dimension (3D) PhC, and/or a hyperbolic metamaterial (HMM). The 2D PhC may include horizontal cylinder bars, vertical cylinder bars, or both. The system, method and device may include a bottom metal reflector that may be Ag free and may act as a bonding layer.
1. A light emitting diode (LED) device comprising:
a light emitting semiconductor layer that in operation emits light having a peak wavelength,
a plurality of indium tin oxide (ITO) layers, and
a reflective structure comprising:
a distributed Bragg reflector (DBR) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-electric (TE) polarization on the reflective structure; and
either:
a photonic crystal (PhC) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-magnetic (TM) polarization on the reflective structure; or
a hyperbolic metamaterial structure (HMM) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with TM polarization on the reflective structure.
2. The LED device of claim 1 wherein the ITO layers are not in direct contact with the PhC nor the HMM.
3. The LED device of claim 1 , wherein the reflective structure comprises the PhC.
4. The LED device of claim 3 , wherein the PhC is a two-dimension (2D) PhC.
5. The LED device of claim 3 , wherein the PhC includes material pairs.
6. The LED device of claim 5 , wherein the material pairs include SiO2 and TiO2.
7. A light emitting diode (LED) device comprising:
a light emitting semiconductor layer that in operation emits light having a peak wavelength,
a reflective structure comprising:
a distributed Bragg reflector (DBR) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-electric (TE) polarization on the reflective structure; and
either:
a three-dimension photonic crystal (3D PhC) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-magnetic (TM) polarization on the reflective structure; or
a hyperbolic metamaterial structure (HMM) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with TM polarization on the reflective structure.
8. The LED device of claim 7 , wherein the reflective structure comprises the 3D PhC and the 3D PhC includes vertical cylinder bars.
9. The device of claim 7 wherein the reflective structure comprises the 3D PhC and the 3D PhC includes at least one of spheres and woodpiles.
10. The LED device of claim 1 , wherein the DBR is in contact with the PhC or the HMM.
11. The LED device of claim 7 , wherein the reflective structure comprises the HMM.
12. The LED device of claim 11 , wherein the HMM is formed by alternating metal/dielectric layers of subwavelength thickness.
13. The LED device of claim 1 , further comprising a bottom metal reflector.
14. The LED device of claim 13 , wherein the bottom metal reflector is Ag free.
15. The LED device of claim 13 , wherein the bottom metal reflector acts as a bonding layer.
16. The LED device of claim 1 , wherein the DBR, the PhC, and the HMM are approximately the same thickness.
17. A light emitting diode device (LED) comprising:
a semiconductor layer formed as a III/V direct bandgap semiconductor that in operation emits light having a peak wavelength;
a reflective structure comprising:
a distributed Bragg reflector (DBR) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-electric (TE) polarization on the reflective structure; and
either:
a photonic crystal (PhC) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with transverse-magnetic (TM) polarization on the reflective structure; or
a hyperbolic metamaterial structure (HMM) configured to highly reflect light emitted by the light emitting semiconductor layer at the peak wavelength and incident with TM polarization on the reflective structure; and
a plurality of indium tin oxide (ITO) layers; and
a bottom metal reflector that is Ag free and a bonding layer.
18. The light emitting diode device of claim 17 , wherein the bottom metal reflector comprises Au.
19. The LED device of claim 1 , wherein the reflective structure comprises the HMM.
20. The LED device of claim 7 , wherein the reflective structure comprises the 3D PhC.