(Al, Ga, In)N and ZnO direct wafer bonded structure for optoelectronic applications, and its fabrication method

• US 20070001186A1
• Filed: 06/16/2006
• Published: 01/04/2007
• Est. Priority Date: 06/17/2005
• Status: Active Grant

• Current Assignee: Japan Science And Technology Agency
• Original Assignee: Japan Science And Technology Agency
• Inventors: Mishra, Umesh, Murai, Akihiko, DenBaars, Steven, McCarthy, Lee, Nakamura, Shoji, Thompson, Daniel, Chen, Christina
• Granted Patent: US 7,719,020 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 5/0215 Bonding to the substrate
• CPC Class Codes: H01S 5/0421 characterised by the semiconducting contacting layers electrodes H01S5/0425
• CPC Class Codes: H01S 5/18347 Mesa comprising active layer
• CPC Class Codes: H01S 5/18369 based on dielectric materials
• CPC Class Codes: H01S 5/1838 Reflector bonded by wafer fusion or by an intermediate compound
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP

Abstract

An (Al, Ga, In)N and ZnO direct wafer bonded light emitting diode (LED), wherein light passes through electrically conductive ZnO. Flat and clean surfaces are prepared for both the (Al, Ga, In)N and ZnO wafers. A wafer bonding process is then performed between the (Al, Ga, In)N and ZnO wafers, wherein the (Al, Ga, In)N and ZnO wafers are joined together and then wafer bonded in a nitrogen ambient under uniaxial pressure at a set temperature for a set duration. After the wafer bonding process, ZnO is shaped for increasing light extraction from inside of LED.

Claims

1. An optical device, comprising:

a III-nitride optoelectronic device comprised of an n-type III-nitride, an active region, and a p-type III-nitride; and

one or more transparent conductor layers wafer bonded to one or more sides of the III-nitride optical device,

wherein light passes through the transparent conductor layers, the transparent conductor layers reduce light absorption inside the III-nitride because they are transparent, and the transparent conductor layers enable uniform light emitting from the active region because they are electrically conductive.

2. The optical device of claim 1, wherein the transparent conductor layers comprises Zn(O, S, Te), Indium Tin Oxide, Gallium Oxide, Indium Gallium Zinc Oxide, In₂O₂/SnO₂ (Indium Tin Oxide, ITO).

3. The optical device of claim 1, wherein the transparent conductor layers are n-type or p-type.

4. The optical device of claim 1, wherein the III-nitride optoelectronic device comprises c-plane III-nitride and the transparent conductor layers are c-plane ZnO layers.

5. The optical device of claim 1, wherein the transparent conductor layers are roughened or shaped.

6. The optical device of claim 5, wherein the roughened or shaped transparent conductor layers reduce light reflections occurring repeatedly inside the LED, and thus extract more light out of the LED.

7. The optical device of claim 5, wherein the transparent conductor layers are ZnO and an O-face of the ZnO'"'"'s surface is shaped.

8. The optical device of claim 5, wherein the transparent conductor layers are shaped to one or more truncated hexagonal pyramids.

9. The optical device of claim 5, wherein the roughened or shaped transparent conductor layers have {10-11} plane surfaces which form a polyhedron.

10. The optical device of claim 1, wherein a polar face of the transparent conductor layers is wafer bonded to a III-nitride wafer.

11. The optical device of claim 1, further comprising an intermediate contact layer deposited on the p-type III-nitride or n-type III-nitride.

12. The optical device of claim 11, wherein the intermediate contact layer comprises an interdigitated contact layer.

13. The optical device of claim 12, wherein the interdigitated contact layer is patterned as a lattice, so that intersititial gaps in the layer pass light through from the III-nitride optical device.

14. The optical device of claim 11, wherein the intermediate contact layer is transparent or translucent.

15. The optical device of claim 11, wherein the intermediate contact layer comprises a bulk contact layer.

16. The optical device of claim 1, further comprising an intermediate contact layer comprising a thin metal or oxidized metal (Pt, Al, Ni, Au, Ni oxide or Ga oxide) inserted between the III-nitride optoelectronic device and the transparent conductor layers that enables less electrical resistance at a wafer bonded interface.

17. The optical device of claim 1, comprising at least one n-type electrode and at least one p-type electrode.

18. The optical device of claim 17, wherein the p-type electrode is formed on n-type ZnO.

19. The optical device of claim 17, wherein the n-type electrode is formed on Ga-faced n-type GaN.

20. The optical device of claim 17, wherein the n-type electrode is formed on N-faced n-type GaN.

21. The optical device of claim 1, wherein the III-nitride optoelectronic device is formed on a suitable substrate.

22. A method for producing a direct wafer bonded optical device, wherein light passes through one or more transparent conductor layers, comprising:

(a) preparing flat and clean surfaces for one or more transparent conductor layers and a III-nitride optoelectronic device to be bonded; and

(b) performing a direct wafer bonding process between the III-nitride optoelectronic device and the transparent conductor layers.

23. The method of claim 22, wherein the transparent conductor layers comprise Zn(O, S, Te), Indium Tin Oxide, Gallium Oxide, Indium Gallium Zinc Oxide, In₂O₂/SnO₂ (Indium Tin Oxide, ITO)

24. The method of claim 22, wherein the III-nitride optoelectronic device and the transparent conductor layers are joined together and then wafer bonded in a nitrogen ambient under uniaxial pressure at a set temperature for a set duration.

25. The method of claim 22, wherein the transparent conductor layers surfaces to be bonded comprise the Zn-face of c-plane ZnO

26. The method of claim 22, wherein the transparent conductor layers surfaces to be bonded comprise the O-face of c-plane ZnO

27. The method of claim 22, wherein the III-nitride optoelectronic device and the transparent conductor layers are loaded into a wafer-bonding furnace, and the furnace is heated to a temperature of 600°

C. for 1 hour in an N₂ gas flow.

28. The method of claim 22, further comprising enhancing electrical conductivity of a wafer bonded interface prior to direct wafer bonding.

29. The method of claim 28, wherein the transparent conductor layers surface is plasma treated prior to the wafer bonding process to enhance electrical conductivity at the wafer bonded interface.

30. The method of claim 22, wherein the III-nitride optoelectronic device surface is partially shaped prior to the wafer bonding process, and thus enables a strong wafer bonded interface.

31. The method of claim 22, wherein a surface of the transparent conductor layers is roughened or shaped after or before the wafer bonding process.

32. The method of claim 31, wherein the surface is an O-face of the ZnO.

33. The method of claim 31, wherein the shaping is by anisotropic etching etching.

34. The method of claim 33, wherein the anisotropic etching comprises a chemical etching.

35. The method of claim 34 wherein the etching is in Hydrochloric Acid (HCL) or diluted HCL.

36. An optical device fabricated by the method of claim 22.