Nanowire LED structure and method for manufacturing the same
View Patent ↗A light emitting diode (LED) structure includes a plurality of devices arranged side by side on a support layer. Each device includes a first conductivity type semiconductor nanowire core and an enclosing second conductivity type semiconductor shell for forming a pn or pin junction that in operation provides an active region for light generation. A first electrode layer extends over the plurality of devices and is in electrical contact with at least a top portion of the devices to connect to the shell. The first electrode layer is at least partly air-bridged between the devices.
1. A light emitting diode (LED) structure, comprising:
a plurality of devices arranged side by side on a support layer, wherein each device comprises a first conductivity type semiconductor nanowire core and an enclosing second conductivity type semiconductor shell for forming a pn or pin junction that in operation provides an active region for light generation, and
a first electrode layer that extends over the plurality of devices and is in electrical contact with at least a top portion of the devices to connect to the shell, wherein the first electrode layer is at least partly air-bridged between the devices, wherein the support layer comprises a n-type semiconductor buffer layer on a substrate, which buffer layer serves as n-contact, and an n-electrode layer which contact the buffer layer.
2. The light emitting diode (LED) structure of claim 1 , wherein the first conductivity type comprises n-type, the second conductivity type comprises p-type and the first electrode layer comprises a p-electrode layer.
3. The light emitting diode (LED) structure of claim 2 , further comprising a second n-electrode layer which electrically connects to the n-type nanowire cores.
4. The light emitting diode (LED) structure of claim 1 , wherein the support layer is reflective.
5. The light emitting diode (LED) structure of claim 1 , wherein the support layer is transparent.
6. The light emitting diode (LED) array of claim 2 , wherein the thickness of the air-bridged p-electrode layer is 150 nm-900 nm.
7. The light emitting diode (LED) structure of claim 1 , wherein the p-electrode is at least partly reflective.
8. The light emitting diode (LED) structure of claim 1 , wherein the p-electrode is transparent.
9. The light emitting diode (LED) structure of claim 8 , wherein at least one other transparent layer is arranged on the p-electrode.
10. The light emitting diode (LED) structure of claim 1 , wherein the LED is flip-chip bonded onto contact electrodes on a carrier.
11. The light emitting diode (LED) structure of claim 1 , further comprising a mirror provided below the nanowire cores.
12. The light emitting diode (LED) structure of claim 11 , wherein the mirror is provided in a recess formed in the substrate, said recess extending to the buffer layer.
13. The light emitting diode (LED) structure of claim 12 , further comprising a plurality of mirrors in a plurality of recesses.
14. The light emitting diode (LED) structure of claim 12 , wherein the mirror comprises a reflective material that partially fills said recess, and wherein a remaining portion of the recess is filled with a filler material providing structural rigidity and high thermal conductivity.
15. The light emitting diode (LED) structure of claim 11 , wherein the mirror is glue bonded to one of the buffer layer and the substrate, and physically bonded to other of the buffer layer and the substrate.
16. The light emitting diode (LED) structure of claim 4 , wherein the support layer comprises a mirror and wherein the mirror is provided in place of a removed n-type semiconductor buffer layer and fully removed substrate.
17. The light emitting diode (LED) structure of claim 2 , wherein each device comprises a nanostructure containing the core, the shell and an active layer between the core and the shell.
18. The light emitting diode (LED) structure of claim 1 , wherein the nanostructure comprises a core-shell nanowire.
19. The light emitting diode (LED) structure of claim 1 , wherein the support layer comprises a semiconductor substrate.
20. The light emitting diode (LED) structure of claim 3 , wherein:
the n-electrode layer comprises an n-pad area on a first part of the buffer layer;
the p-electrode layer comprises a p-pad area on the nanowires in a LED active area or on a dielectric masking layer on the buffer layer adjacent to the nanowires in the LED active area; and
the n-pad area and the p-pad area are separated by a non active area comprising dummy nanowires which do not contact the p-electrode.
21. A top emitting light emitting diode (LED) structure, comprising:
a plurality of devices located on a first surface of a support layer, the devices comprising a semiconductor nanowire core of a first conductivity type and a semiconductor shell of a second conductivity type;
a first transparent electrode which is electrically connected to the shells of the devices, wherein the first electrode layer is at least partly air-bridged between the devices;
a second electrode located in electrical contact with the first surface of the support layer and electrically connected to the cores of the devices through the support layer;
a carrier attached to the device;
a first contact electrically connecting the carrier to a first pad area of the first electrode;
a second contact electrically connecting the carrier to a second pad area of the second electrode; and
a reflective layer located below the cores of the devices, wherein the carrier substrate is located below the reflective layer.
22. The light emitting diode (LED) structure of claim 21 , wherein:
the nanowires have a base end and a tip end;
the base end is attached to the support layer comprising a growth substrate or a buffer layer; and
the first electrode extends from the tip end of the nanowires down between the nanowires.
23. The light emitting diode (LED) structure of claim 22 , wherein the device comprises an air gap in spaces between the nanowires between the first electrode and the support layer.
24. The light emitting diode (LED) structure of claim 21 , wherein the first conductivity type is n-type, the second conductivity type is p-type, and the semiconductor core and the semiconductor shell comprise a III-nitride semiconductor material nanowire.
25. The light emitting diode (LED) structure of claim 21 , further comprising a dielectric masking layer with openings located on the first surface of the support layer such that the cores electrically contact the first surface of the support layer through the openings and the shells are electrically isolated from the first surface of the support layer by the masking layer.
26. The light emitting diode (LED) structure of claim 25 , wherein:
the first electrode pad area is located between the nanowires on the masking layer; and
the second electrode pad area is located on the first surface of the support layer between the nanowires in an opening in the masking layer.