Thin-film LED array with low refractive index patterned structures and reflector
Described are light emitting diode (LED) devices having a patterned dielectric layer on a substrate and methods for effectively growing epitaxial III-nitride layers on them. A nucleation layer, comprising a III-nitride material, is grown on a substrate before any patterning takes place. The patterned dielectric layer comprises a first plurality of features and a second plurality of features, where the second plurality of features has a height larger than the height of the first plurality of features. The second plurality of features aligns with the cathode layer of the trench.
1 . A light emitting diode (LED) device comprising:
a nucleation layer on a substrate, the nucleation layer comprising a first III-nitride material;
a patterned dielectric layer on a top surface of the nucleation layer, the patterned dielectric layer comprising a first plurality of features, a second plurality of features adjacent the first plurality of features, and a plurality of spaces between the first plurality of features and the second plurality of features, the first plurality of features and the second plurality of features protruding from a top surface of the nucleation layer, the second plurality of features having a second height greater than a first height of the first plurality of features, and the plurality of spaces exposing a top surface of the nucleation layer;
a reflector layer on a surface of the second plurality of features distal from the nucleation layer;
a III-nitride layer on the first plurality of features and on the plurality of spaces, the III-nitride layer comprising a second III-nitride material; and
a metal contact aligned with and directly contacting the second plurality of features.
2 . The light emitting diode device of claim 1 , wherein the first plurality of features and the second plurality of features independently have a shape selected from a hemispherical shape, a triangular pyramidal shape, a quadrangular pyramidal shape, a hexagonal pyramidal shape, a conical shape, a semi-spherical shape, or a cut-spherical shape.
3 . The light emitting diode device of claim 1 , wherein the first height is in a range of from 10 nm to 3 μm.
4 . The light emitting diode device of claim 1 , wherein the second height is about 10% to 90% of a thickness of the III-nitride layer.
5 . The light emitting diode device of claim 1 , wherein the second plurality of features has a second width greater than a first width of the first plurality of features.
6 . The light emitting diode device of claim 5 , wherein the first width is in a range of from 5 nm to 3 μm and the second width is in a range of from 100 nm to 5 μm.
7 . The light emitting diode device of claim 1 , wherein the first plurality of features has a first width greater than a second width of the second plurality of features.
8 . The light emitting diode device of claim 1 , wherein the reflector layer comprises a distributed Bragg reflector (DBR).
9 . The light emitting diode device of claim 1 , wherein the first III-nitride material and the second III-nitride material independently comprise one or more of aluminum, gallium, and indium.
10 . The light emitting diode device of claim 9 , wherein the first III-nitride material and the second III-nitride material are the same.
11 . The light emitting diode device of claim 1 , wherein the dielectric layer comprises a low refractive index material having a refractive index in a range of from about 1.2 to about 2.
12 . The light emitting diode device of claim 11 , wherein the dielectric layer comprises one or more of silicon oxide (SiO 2 ) and silicon nitride (Si 3 N 4 ).
13 . The light emitting diode device of claim 1 , wherein the second III-nitride material comprises gallium nitride (GaN).
14 . The light emitting diode device of claim 1 , wherein the nucleation layer has a thickness in a range of from about 5 nm to about 100 nm.
15 . A method of manufacturing the light emitting diode device of claim 1 , the method comprising:
depositing the nucleation layer on the substrate, the nucleation layer comprising the first III-nitride material;
depositing the dielectric layer on the top surface of the nucleation layer, the dielectric layer comprising the low refractive index dielectric material;
patterning the dielectric layer to form the patterned surface having the first plurality of features, the second plurality of features adjacent the first plurality of features, and having the plurality of spaces between the first plurality of features and the second plurality of features, the first plurality of features and the second plurality of features protruding from the top surface of the nucleation layer, the second plurality of features having the second height and the second width greater than the first height and the first width of the first plurality of features, and the plurality of spaces exposing the top surface of the nucleation layer;
depositing the reflector layer on the surface of the second plurality of features distal from the nucleation layer;
epitaxially growing the III-nitride layer on the patterned surface, the III-nitride layer comprising the second III-nitride material; and
forming the metal contact aligned with and directly contacting the second plurality of features.
16 . The method of claim 15 , wherein the first plurality of features and the second plurality of features independently have a shape selected from a hemispherical shape, a triangular pyramidal shape, a quadrangular pyramidal shape, a hexagonal pyramidal shape, a conical shape, a semi-spherical shape, or a cut-spherical shape.
17 . The method of claim 15 , wherein the first height is in a range of from 10 nm to 3 μm and the first width is in a range of from 5 nm to 3 μm.
18 . The method of claim 15 , wherein the second height is about 10% to 90% of a thickness of the Ill-nitride layer.
19 . The method of claim 15 , wherein the nucleation layer is deposited by one or more of sputter deposition, atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma enhanced atomic layer deposition (PEALD), and plasma enhanced chemical vapor deposition (PECVD).
20 . The method of claim 15 , wherein the dielectric layer comprises a low refractive index material having a refractive index in a range of from about 1.2 to about 2.