NANOWIRE LED STRUCTURE AND METHOD FOR MANUFACTURING THE SAME

• US 20110309382A1
• Filed: 06/17/2011
• Published: 12/22/2011
• Est. Priority Date: 06/18/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Glo AB (Shoei Electronic Materials, Inc.)
• Inventors: LÔWGREN, Truls
• Granted Patent: US 8,669,125 B2
• Time in Patent Office: Days
• US Class Current: 257/88
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/18 within the light emitting region
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: Y10S 977/762 Nanowire or quantum wire, i.e. axially elongated structure having two dimensions of 100 nm or less

Abstract

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.

Claims

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.

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 3, wherein the support layer comprises a n-type semiconductor buffer layer on a substrate, which buffer layer serves as n-contact, and the n-electrode layer contacts the buffer layer.

5. The light emitting diode (LED) structure of claim 1, wherein the support layer is reflective.

6. The light emitting diode (LED) structure of claim 1, wherein the support layer is transparent.

7. The light emitting diode (LED) array of claim 2, wherein the thickness of the air-bridged p-electrode layer is 150 nm-900 nm.

8. The light emitting diode (LED) structure of claim 1, wherein the p-electrode is at least partly reflective.

9. The light emitting diode (LED) structure of claim 1, wherein the p-electrode is transparent.

10. The light emitting diode (LED) structure of claim 9, wherein at least one other transparent layer is arranged on the p-electrode.

11. The light emitting diode (LED) structure of claim 1, wherein the LED is flip-chip bonded onto contact electrodes on a carrier.

12. The light emitting diode (LED) structure of claim 4, further comprising a mirror provided below the nanowire cores.

13. The light emitting diode (LED) structure of claim 12, wherein the mirror is provided in a recess formed in the substrate, said recess extending to the buffer layer.

14. The light emitting diode (LED) structure of claim 13, further comprising a plurality of mirrors in a plurality of recesses.

15. The light emitting diode (LED) structure of claim 13, 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.

16. The light emitting diode (LED) structure of claim 12, 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.

17. The light emitting diode (LED) structure of claim 5, 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.

18. 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.

19. The light emitting diode (LED) structure of claim 1, wherein the nanostructure comprises a core-shell nanowire.

20. The light emitting diode (LED) structure of claim 1, wherein the support layer comprises a semiconductor substrate.

21. 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.

22. A method of manufacturing a nanowire light emitting diode (LED) structure, comprising:

providing a support layer;

providing a plurality of devices arranged side by side on the 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;

depositing a sacrificial layer that completely covers the devices in a non-active area and partially covers the devices in a LED area, leaving top portions of the devices in the LED area exposed; and

depositing a first electrode layer on the exposed top portions of the devices and over the support layer between the devices.

23. The method of claim 22, 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.

24. The method of claim 23, further comprising depositing a second n-electrode layer which electrically connects to the n-type nanowire cores.

25. The method of claim 24, wherein the support layer comprise an n-type semiconductor buffer layer on a substrate, which buffer layer serves as n-contact and the n-electrode layer contacts the buffer layer.

26. The nanowire method of claim 24, wherein the support layer comprises at least one of a transparent layer, a reflective layer or a semiconductor substrate.

27. The method of claim 25, wherein each device comprises a core-shell nanowire containing the core, the shell and an active layer between the core and the shell.

28. The method of claim 27, further comprising a dielectric masking layer on the support layer such that the cores protrude from the buffer layer through openings in the masking layer, and the shells are located on the masking layer.

29. The method of claim 28, further comprising removing the sacrificial layer such that a first portion of the first electrode layer located on the sacrificial layer in the non-active area is removed and a second portion of the first electrode layer located on top of the nanowire shells forms an air-bridged p-electrode.

30. The method of claim 29, wherein the sacrificial layer comprises a photoresist.

31. The method of claim 25, wherein the buffer layer comprises at least one of gallium nitride or aluminum gallium nitride.

32. The method of claim 23, wherein the p-electrode comprises a transparent conductive oxide layer.

33. The method as claimed in claim 29, further comprising the step of temporary bonding a carrier to the side of the structure comprising the nanowires.

34. The method as claimed in claim 33, further comprising the step of etching one or more recesses in the substrate down to the buffer layer.

35. The method as claimed in claim 34, further comprising forming a mirror on the buffer layer in the at least one recess to render the LED structure top emitting.

36. The method as claimed in claim 35, further comprising filling the at least one recess over the mirror with a filler material and removing the structure from the carrier.

37. The method as claimed in claim 33, further comprising removing the substrate from the structure leaving the buffer layer exposed and applying a mirror to the buffer layer to render the LED structure top emitting.

38. The method as claimed in claim 37, further comprising attaching a carrier to the mirror.

39. The method as claimed in claim 29, further comprising attaching a carrier to the structure, the carrier having a mirror on one surface facing the buffer layer.

40. 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;

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;

41. The light emitting diode (LED) structure of claim 40, 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.

42. The light emitting diode (LED) structure of claim 41, wherein the device comprises an air gap in spaces between the nanowires between the first electrode and the support layer.

43. The light emitting diode (LED) structure of claim 40, 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.

44. The light emitting diode (LED) structure of claim 40, 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.

45. The light emitting diode (LED) structure of claim 44, 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.

46. A method of making a top emitting light emitting (LED) structure, comprising:

forming 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;

forming a first transparent electrode which is electrically connected to the shells of the devices;

forming 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;

providing a reflective layer below the cores of the devices and a carrier which is attached to the structure below the reflective layer;

forming a first contact electrically connecting the carrier to a first pad area of the first electrode; and

forming a second contact electrically connecting the carrier to a second pad area of the second electrode.