Nanostructured LED
View Patent ↗The device according to the invention comprises a nanostructured LED with a first group of nanowires protruding from a first area of a substrate and a contacting means in a second area of the substrate. Each nanowire of the first group of nanowires comprises a p-i-n-junction and a top portion of each nanowire or at least one selection of nanowires is covered with a light reflecting contact layer. The contacting means of the second area is in electrical contact with the bottom of the nanowires, the light-reflecting contact layer being in electrical contact with the contacting means of the second area via the p-i-n-junction. Thus when a voltage is applied between the contacting means of the second area and the light-reflecting contact layer, light is generated within the nanowire. On top of the light-reflecting contact layer, a first group of contact pads for flip-chip bonding can be provided, distributed and separated to equalize the voltage across the layer to reduce the average serial resistance.
1. A nanostructured LED comprising:
a plurality of nanowires protruding from a substrate through openings in a mask layer, each nanowire comprising a pn- or p-i-n-junction that is formed between an n-doped core that comprises an n-doped III-V semiconductor material and protrudes upward vertically from a top surface of the substrate and a p-doped shell that laterally surrounds the n-doped core and overlies a top portion of the n-doped core and a respective proximal portion of the mask layer around a respective opening therein so that the pn or p-i-n junction includes a vertically extending portion that laterally surrounds the n-doped core and extends perpendicular to the top surface of the substrate,
wherein a first group of multiple nanowires within the plurality of nanowires is covered with a laterally-extending portion of a continuous portion of a light-reflecting or transparent contact layer located within a respective area,
wherein the continuous portion of the light-reflecting or transparent contact layer further includes vertical portions that extend downward from the laterally-extending portion between vertically extending portions of pn or p-i-n junctions of the first group of multiple nanowires and electrically contact outer sidewalls of p-doped shells of the first group of multiple nanowires,
wherein a conductive material continuously extends along an interface between the light-emitting or transparent contact layer underneath the laterally-extending portion of the continuous portion of the light-reflecting or transparent contact layer, along and in contact with the sidewalls of the p-doped shells of the nanowires, and directly on the top surface of the mask layer,
and wherein a second group of at least one nanowire within the plurality of nanowires is located outside of the at least one area of, and is not contacted by, any material of the light-reflecting or transparent contact layer and is electrically dead; and
a first group of at least one contact pad that is in electrical contact with a bottom portion of each of the plurality of nanowires,
wherein the light-reflecting or transparent contact layer is in electrical contact with the pn- or p-i-n-junctions.
2. The nanostructured LED according to claim 1 , wherein the substrate comprises a buffer layer between a substrate material and the plurality of nanowires.
3. The nanostructured LED according to claim 1 , wherein the light-reflecting or transparent contact layer defines a plurality of contact groups of nanowires that are laterally spaced apart.
4. The nanostructured LED according to claim 1 , further comprising a second group of at least another contact pad in contact with a respective portion of the light-reflecting or transparent contact layer and distributed on top of a surface formed by the light-reflecting or transparent contact layer.
5. The nanostructured LED according to claim 4 , wherein one or more contact pads in the second group of at least another contact pad is in individual contact with at least one contact group of nanowires such that the at least one contact group of nanowires can be addressed individually and independently of other groups of nanowires.
6. The nanostructured LED according to claim 4 , further comprising a carrier structure which is bonded to the first group of at least one contact pad and second group of at least another contact pad.
7. The nanostructured LED according to claim 4 , wherein the first group of multiple nanowires or the second group of at least one nanowire forms an array of nanowires.
8. The nanostructured LED according to claim 4 , further comprising:
a carrier structure;
a first plurality of bumps electrically connecting the first group of at least one contact pad to the carrier structure; and
a second plurality of bumps electrically connecting a second group of at least another contact pad to the carrier structure.
9. The nanostructured LED according to claim 8 , wherein:
the substrate comprises a light-transmissive buffer layer;
each of the plurality of nanowires protrudes from a first surface of the buffer layer;
the first group of at least one contact pad is located on the first surface of the buffer layer;
a phosphor is located over a second surface of the buffer layer;
the light-reflecting or transparent contact layer comprises a light-reflecting contact layer; and
the second group of at least another contact pad is located on the light-reflecting contact layer.
10. A nanostructured LED of claim 4 , further comprising:
a first plurality of bumps electrically connecting the first group of at least one contact pad to a carrier structure; and
a second plurality of bumps electrically connecting the second group of at least another contact pad to the carrier structure.
11. The nanostructured LED according to claim 10 , wherein:
the substrate comprises a light-transmissive buffer layer;
each of the plurality of nanowires protrudes from a first surface of the buffer layer;
the first group of at least one contact pad is located on the first surface of the buffer layer;
a phosphor is located over a second surface of the buffer layer; and
the second group of at least another contact pad is located on the light-reflecting or transparent contact layer.
12. The nanostructured LED according to claim 1 , wherein the plurality of nanowires contains a plurality of contact groups of nanowires that can be addressed individually and independently of other contact groups of nanowires.
13. The nanostructured LED according to claim 2 , wherein the first group of at least one contact pad comprises a plurality of contact pads that are connected through the buffer layer.
14. The nanostructured LED according to claim 1 , wherein the plurality of nanowires and the first group of at least one contact pad are located on the same side of the substrate.
15. The nanostructured LED according to claim 1 , wherein the light-reflecting or transparent contact layer comprises an aluminium or silver light-reflecting contact layer.
16. The nanostructured LED according to claim 1 , wherein the light-reflecting or transparent contact layer comprises a Zn x O 1-x or In x Sn y O 1-x-y transparent contact layer.
17. The nanostructured LED according to claim 1 , further comprising a carrier structure that is glued to the substrate.
18. The nanostructured LED according to claim 1 , wherein:
each of the plurality of nanowires protrudes from a first surface of the substrate;
a phosphor is located over the plurality of nanowires protruding from the first surface of the substrate; and
the light-reflecting or transparent contact layer comprises a transparent contact layer.