LED ON SILICON SUBSTRATE USING ZINC-SULFIDE AS BUFFER LAYER
A vertical GaN-based blue LED has an n-type GaN layer that was grown over a ZnS layer that in turn was grown directly on a silicon substrate. In one example, the ZnS layer is a transitional buffer layer that is 50 nm thick, and the n-type GaN layer is at least 2000 nm thick. Growing the n-type GaN layer on the ZnS buffer layer reduces lattice defect density in the n-type layer. The ZnS buffer layer provides a good lattice constant match with the silicon substrate and provides a compound polar template for subsequent GaN growth. After the epitaxial layers of the LED are formed, a conductive carrier is wafer bonded to the structure. The silicon substrate and the ZnS buffer layer are then removed. Electrodes are added and the structure is singulated to form finished LED devices.
1 . A method of manufacturing a Light Emitting Diode (LED) device, comprising:
(a) forming a zinc-sulfide (ZnS) layer over and directly on a silicon substrate; and
(b) forming an epitaxial LED structure over the ZnS layer, wherein the epitaxial LED structure comprises an active layer disposed between a p-type layer and an n-type layer, and wherein the silicon substrate, the ZnS layer, and the epitaxial LED structure form a first structure.
2 . The method of manufacturing of claim 1 , further comprising:
(c) bonding a conductive carrier to the first structure thereby forming a second structure; and
(d) removing the silicon substrate and the ZnS layer from the second structure thereby forming a third structure.
3 . The method of manufacturing of claim 2 , further comprising:
after (d) roughening a surface of the n-type layer of the epitaxial LED structure.
4 . The method of manufacturing of claim 2 , wherein the bonding of (c) involves using a eutectic bond metal layer to wafer bond a carrier wafer structure to the first structure, and wherein the conductive carrier is a part of the carrier wafer structure.
5 . The method of manufacturing of claim 2 , further comprising:
(e) forming electrodes on the third structure; and
(f) singulating the third structure thereby forming the LED device.
6 . The method of manufacturing of claim 1 , further comprising:
after (a) forming an aluminum-nitride (AlN) layer over the ZnS layer, and then forming an aluminum-gallium-nitride (AlGaN) layer over the AlN layer, wherein the ZnS layer, the AlN layer, and the AlGaN layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.
7 . The method of manufacturing of claim 1 , further comprising:
after (a) forming a template layer over the ZnS layer, wherein the n-type layer of the epitaxial LED structure is formed over the template layer.
8 . The method of manufacturing of claim 1 , wherein the n-type layer of the epitaxial LED structure has a thickness of at least two thousand nanometers.
9 . The method of manufacturing of claim 1 , wherein the ZnS layer is less than one hundred nanometers thick.
10 . The method of manufacturing of claim 1 , further comprising:
after (a) forming a zinc-telluride (ZnTe) layer over the ZnS layer, wherein the ZnS layer and the ZnTe layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.
11 . The method of manufacturing of claim 10 , wherein the ZnTe layer is formed directly on the ZnS layer.
12 . The method of manufacturing of claim 1 , further comprising:
after (a) forming a boron-nitride (BN) layer over the ZnS layer, wherein the ZnS layer and the BN layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.
13 . An apparatus, comprising:
a silicon substrate;
a Zinc-Sulfide (ZnS) layer formed directly on the silicon substrate; and
an epitaxial Light Emitting Diode (LED) structure formed on the ZnS layer, wherein the epitaxial LED structure comprises an active layer disposed between a p-type layer and an n-type layer.
14 . The apparatus of claim 13 , further comprising:
an aluminum-nitride (AlN) layer formed over the ZnS layer; and
an aluminum-gallium-nitride (AlGaN) layer formed over the AlN layer, wherein the ZnS layer, the AlN layer, and the AlGaN layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.
15 . The apparatus of claim 13 , further comprising:
a template layer formed over the ZnS layer, wherein the epitaxial LED structure is formed over the template layer.
16 . The apparatus of claim 13 , wherein the ZnS layer is less than one hundred nanometers thick.
17 . The apparatus of claim 13 , wherein the n-type layer of the epitaxial LED structure has a thickness of at least two thousand nanometers.
18 . The apparatus of claim 13 , further comprising:
a zinc-telluride (ZnTe) layer formed over the ZnS layer, wherein the ZnS layer and the ZnTe layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.
19 . The apparatus of claim 18 , wherein the ZnTe layer is formed directly on the ZnS layer.
20 . The apparatus of claim 13 , further comprising:
a boron-nitride (BN) layer formed over the ZnS layer, wherein the ZnS layer and the BN layer form a buffer layer, and wherein the epitaxial LED structure is formed over the buffer layer.