High efficiency light emitting diodes
View Patent ↗The present disclosure relates to high efficiency light emitting diode devices and methods for fabricating the same. In accordance with one or more embodiments, a light emitting diode device includes a substrate having one or more recessed features formed on a surface thereof and one or more omni-directional reflectors formed to overlie the one or more recessed features. A light emitting diode layer is formed on the surface of the substrate to overlie the omni-directional reflector. The one or more omni-directional reflectors are adapted to efficiently reflect light.
1. A light emitting diode device comprising:
a substrate having a surface;
an interlayer formed on the surface of the substrate, the interlayer comprising a non-gallium-nitride (GaN) material including at least one of silicon (Si) or silicon-carbide (SiC);
a recessed feature disposed in the interlayer;
an omni-directional reflector disposed at least partially within the recessed feature, the omni-directional reflector adapted to efficiently reflect light; and
a light emitting diode layer disposed over the surface of the substrate, including over the omni-directional reflector.
2. The device of claim 1 , wherein the substrate comprises at least one of a sapphire substrate, silicon (Si) substrate, silicon-carbide (SiC) substrate, and a gallium-nitride (GaN) substrate.
3. The device of claim 1 , wherein:
the recessed feature includes a bottom portion and sidewall portions that extend at an inclined angle from the bottom portion to the surface of the interlayer, the bottom portion being disposed at a depth in the interlayer; and
the omni-directional reflector is disposed on the sidewall portions and the bottom portion of the recessed feature.
4. The device of claim 3 , wherein:
the inclined angle of the sidewall portions is about 45° to about 90°, and
the depth of the bottom portion is about 100 nm to about 2.5 μM.
5. The device of claim 1 , wherein the omni-directional reflector comprises a plurality of material layers combined to have a reflectivity of 80% or greater of a particular emission wavelength.
6. The device of claim 1 , wherein the omni-directional reflector comprises a plurality of material layers combined to efficiently reflect light of a particular emission wavelength including at least one wavelength between 400 nm and 550 nm.
7. The device of claim 1 , wherein:
the omni-directional reflector comprises a plurality of material layers, and
each material layer comprises a dielectric material including at least one of silicon-oxide (SiO 2 ), tantalum-oxide (Ta 2 O 5 ), titanium-oxide (TiO 2 ), hafnium-oxide (HfO 2 ), niobium-oxide (Nb 2 O 5 ), cerium-oxide (CeO 2 ), zirconium-oxide (ZrO 2 ), calcium-fluoride (CaF 2 ), and silicon-nitride (Si 3 N 4 ).
8. The device of claim 1 , wherein the light emitting diode layer comprises at least one gallium-nitride (GaN) layer in contact with the surface of the substrate interlayer.
9. The device of claim 1 , wherein the light emitting diode layer comprises one or more epitaxial layers including at least one of an n-doped layer, a quantum well active layer, and a p-doped layer.
10. A light emitting diode device comprising:
a substrate having a surface;
an interlayer formed on the surface of the substrate, the interlayer comprising a non-gallium-nitride (GaN) material including at least one of silicon (Si) or silicon-carbide (SiC);
a plurality of recessed features formed in the interlayer;
a plurality of omni-directional reflectors disposed on sidewalls and bottom surfaces of corresponding recessed features, the omni-directional reflectors adapted to efficiently reflect light; and
a light emitting diode layer disposed over the surface of the substrate, including over the omni-directional reflectors,
wherein each recessed feature includes a bottom portion and sidewall portions that extend at an inclined angle from the bottom portion to the surface of the substrate, the bottom portion being disposed at a depth in the substrate, and
wherein each omni-directional reflector is disposed on the sidewall portions and the bottom portion of corresponding recessed features.
11. The device of claim 10 , wherein the predetermined emission wavelength includes at least one wavelength between 400 nm and 550 nm.
12. The device of claim 10 , wherein:
the bottom portion of each recessed feature has a flat surface;
the inclined angle of the sidewall portions of each recessed feature is about 45° to about 90°, and
the depth of the bottom portion is about 100 nm to about 2.5 μm.
13. The device of claim 10 , wherein:
each omni-directional reflector comprises a plurality of alternatingly repeated material layers, and
each material layer comprises a dielectric material including at least one of silicon-oxide (SiO 2 ), tantalum-oxide (Ta 2 O 5 ), titanium-oxide (TiO 2 ), hafnium-oxide (HfO 2 ), niobium-oxide (Nb 2 O 5 ), cerium-oxide (CeO 2 ), zirconium-oxide (ZrO 2 ), calcium-fluoride (CaF 2 ), and silicon-nitride (Si 3 N 4 ).
14. The device of claim 10 , wherein the light emitting diode layer comprises:
at least one gallium-nitride (GaN) layer in contact with the surface of the interlayer, and
a plurality of epitaxial layers including an n-doped layer, a quantum well active layer, and a p-doped layer; and
wherein the plurality of omni-directional reflectors correspond to different lateral growth conditions.
15. A method of fabricating a light emitting diode comprising:
providing a substrate having a surface;
an interlayer formed on the surface of the substrate, the interlayer comprising a non-gallium-nitride (GaN) material including at least one of silicon (Si) or silicon-carbide (SiC);
forming a recessed feature within the interlayer, the recessed feature being defined by a bottom portion and sidewall portions that extend at an inclined angle from the bottom portion to the surface of the substrate, and the bottom portion being disposed at a depth in the substrate;
forming a omni-directional reflector over the recessed feature, the omni-directional reflector adapted to efficiently reflect light; and
forming a light emitting diode layer on the surface of the substrate and over the omni-directional reflectors.
16. The method of claim 15 , wherein:
the substrate comprises at least one of a sapphire substrate, silicon (Si) substrate, silicon-carbide (SiC) substrate, and a gallium-nitride (GaN) substrate,
the forming the recessed feature includes etching a recess that extends into the substrate from the surface of the substrate, and
the omni-directional reflector being formed on the sidewall portions and the bottom portion of the recessed feature.
17. The method of claim 16 , wherein:
the inclined angle of the sidewall portions is about 45° to about 90°, and
the bottom portion of the recessed feature is etched to the depth of about 100 nm to about 2.5 μm.
18. The method of claim 15 , wherein:
the forming the omni-directional reflector comprises forming a plurality of material layers combined to have a reflectivity of 80% or greater of a particular emission wavelength, and
each material layer comprises a dielectric material including at least one of silicon-oxide (SiO 2 ), tantalum-oxide (Ta 2 O 5 ), titanium-oxide (TiO 2 ), hafnium-oxide (HfO 2 ), niobium-oxide (Nb 2 O 5 ), cerium-oxide (CeO 2 ), zirconium-oxide (ZrO 2 ), calcium-fluoride (CaF 2 ), and silicon-nitride (Si 3 N 4 ).
19. The method of claim 15 , wherein the forming the light emitting diode layer comprises:
forming at least one gallium-nitride (GaN) layer in contact with the surface of the interlayer, and
forming a plurality of epitaxial layers including an n-doped layer, a quantum well active layer, and a p-doped layer.
20. The method of claim 15 , wherein the forming the recessed feature is performed such that the bottom portion of the recessed feature includes a flat surface.