Method for fabricating group-III nitride devices and devices fabricated using method

• US 7,332,365 B2
• Filed: 05/18/2004
• Issued: 02/19/2008
• Est. Priority Date: 05/18/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Swoboda, Chuck, Mishra, Umesh, Nakamura, Shuji, Edmond, John, DenBaars, Steven
• Primary Examiner(s): Picardat; Kevin M.
• Application Number:
  US10/848,937
• Publication Number:
  US 20060049411A1
• Time in Patent Office: 1,372 Days
• Field of Search: 438/22, 438/29, 438/39, 438/40, 438/41, 438/44, 438/46, 438/47, 257/79, 257/86, 257/94, 257/98
• US Class Current: 438/29
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/105 with a resonant cavity structure
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/465 with a resonant cavity structure

Abstract

A method according to the present invention for fabricating high light extraction photonic devices comprising growing an epitaxial semiconductor structure on a substrate and depositing a first mirror layer on the epitaxial semiconductor structure such that the epitaxial semiconductor structure is sandwiched between the first mirror layer and the substrate. Flip-chip mounting the epitaxial semiconductor structure, with its first mirror and substrate on a submount such that the epitaxial semiconductor device structure is sandwiched between the submount and substrate. The substrate is then removed from the epitaxial structure by introducing an etch environment to the substrate. A second mirror layer is deposited on the epitaxial semiconductor structure such that the epitaxial semiconductor structure is sandwiched between the first and second mirror layers. A device according to the present invention comprising a resonant cavity light emitting diode (RCLED) mounted to a submount.

Claims

1. A method for fabricating high light extraction photonic devices, comprising:

growing a Group-III nitride epitaxial semiconductor device structure on a silicon carbide (SiC) substrate, said epitaxial semiconductor structure and substrate comprising an emitter adapted to emit light in response to a bias;

flip-chip mounting said emitter on a submount such that said epitaxial semiconductor device structure is sandwiched between said submount and said substrate, and

etching said substrate off said epitaxial semiconductor device by utilizing an etch environment that etches said substrate substantially faster than said epitaxial semiconductor structure.

2. The method of claim 1, wherein said substrate comprises a monocrystalline material.

3. The method of claim 1, wherein said substrate comprises monocrystalline silicon carbide (SiC).

4. The method of claim 1, wherein said etch environment comprises a reactive ion etch.

5. The method of claim 1, wherein said etch environment comprises nitrogen trifluoride (NF₃).

6. The method of claim 1, further comprising depositing a first mirror layer on said epitaxial semiconductor structure opposite said substrate structure prior to said flip-chip mounting of said emitter, said mirror sandwiched between said epitaxial semiconductor structure and said submount after said flip-chip mounting.

7. The method of claim 6, wherein said first mirror layer comprises a reflective metal.

8. The method of claim 6, wherein said first mirror layer comprises a distributed Bragg reflector (DBR) comprising a plurality of alternating layer pairs of dielectric material.

9. The method of claim 8, wherein each of said layer pairs comprise a layer of silicon dioxide (SiO₂) and a layer of titanium dioxide (TiO₂), or a layer of silicon dioxide (SiO₂) and a layer of tantalum pentoxide (Ta₂O₅), said pairs of layers having a thickness approximately equal to a quarter of said wavelength of said emitted light.

10. The method of claim 8, wherein said layer pairs repeat two to four times.

11. The method of claim 6, wherein said first mirror layer comprises an epitaxial DBR comprising a plurality of alternating layer pairs of epitaxial material.

12. The method of claim 11, wherein each of said alternating layer pairs comprises a layer of gallium nitride (GaN) and a layer of aluminum nitride (AlN), or a layer of gallium nitride (GaN) and a layer of an alloy of aluminum nitride (Al_zX_yN), said alternating layer pairs having a thickness approximately equal to a quarter of said wavelength of said emitted light.

13. The method of claim 11, wherein said pairs of layers repeats eight to twelve times.

14. The method of claim 1, wherein said submount comprises one of the materials from the group consisting of silicon carbide (SiC), silicon, sapphire, metal and glass.

15. The method of claim 1, further comprising depositing a second mirror layer on said epitaxial semiconductor structure after said substrate has been etched, said second mirror layer arranged such that said epitaxial semiconductor structure is sandwiched between said submount and said second mirror layer.

16. The method of claim 15, wherein said second mirror layer comprises a reflective metal.

17. The method of claim 15, wherein said second mirror layer comprises a distributed Bragg reflector (DBR) comprising a plurality of alternating layer pairs of dielectric material.

18. The method of claim 17, wherein each of said layer pairs comprise a layer of silicon dioxide (SiO₂) and a layer of titanium dioxide (TiO₂), or a layer of silicon dioxide (SiO₂) and a layer of tantalum pentoxide (Ta₂O₅), the thickness of said layer pairs equal to approximately a quarter of said wavelength of said emitted light.

19. The method of claim 17, wherein said layer pairs repeat two to four times.

20. The method of claim 15, wherein said second mirror layer comprises an epitaxial DBR comprising a plurality of alternating layer pairs of epitaxial material.

21. The method of claim 20, wherein each of said alternating layer pairs comprises a layer of gallium nitride (GaN) and a layer of aluminum nitride (AlN), or a layer of gallium nitride (GaN) and a layer of an alloy of aluminum nitride (Al_zX_yN), said alternating layer pairs having a thickness approximately equal to a quarter of said wavelength of said emitted light.

22. The method of claim 20, wherein said pairs of layers repeats eight to twelve times.

23. The method of claim 1, wherein growing an epitaxial semiconducting structure comprises:

growing a first epitaxial semiconductor layer on said substrate, and

growing a second epitaxial semiconductor layer on said first epitaxial semiconductor layer, such that said first semiconductor layer is sandwiched between said substrate and said second semiconductor layer.

24. The method of claim 23, wherein growing an epitaxial semiconducting structure comprises growing thin doped layers and forming a resonant cavity light emitting diode.

25. A method for fabricating high light extraction photonic devices, comprising:

growing an epitaxial semiconductor structure on a silicon carbide substrate;

depositing a first mirror layer on said epitaxial semiconductor structure such that said epitaxial semiconductor structure is sandwiched between said first mirror layer and said substrate;

removing said substrate from said epitaxial structure by introducing an etch environment to said substrate; and

depositing a second mirror layer on said epitaxial semiconductor structure such that said epitaxial semiconductor structure is sandwiched between said first and second mirror layers.

26. The method of claim 25, wherein said etch environment etches said substrate substantially faster than said epitaxial semiconducting structure, etching off substantially all of said substrate without etching off substantially any of said epitaxial semiconducting structure.

27. The method of claim 25, wherein said epitaxial semiconductor structure is adapted to emit light in response to an electrical signal.

28. The method of claim 25, wherein said epitaxial semiconductor structure comprises a Group-III nitride semiconductor material.

29. The method of claim 25, wherein said substrate comprises monocrystalline silicon carbide (SiC).

30. The method of claim 25, wherein said etch environment comprises a reactive ion etch.

31. The method of claim 25, wherein said etch environment comprises nitrogen trifluoride (NF₃).

32. The method of claim 25, wherein either of said first or second mirror layers comprise a reflective metal.

33. The method of claim 25, wherein said either first or second mirror layer comprise distributed Bragg reflector (DBR) mirror having alternating layer pairs of dielectric material.

34. The method of claim 33, wherein each of said layer pairs comprise a layer of silicon dioxide (SiO₂) and a layer of titanium dioxide (TiO₂), or a layer of silicon dioxide (SiO₂) and a layer of tantalum pentoxide (Ta₂O₅).

35. The method of claim 25, wherein either of said first or second mirror layers comprise an epitaxial DBR mirror alternating layer pairs of epitaxial material.

36. The method of claim 35, wherein each of said alternating layer pairs comprises a layer of gallium nitride (GaN) and a layer of aluminum nitride (AlN), or a layer of gallium nitride (GaN) and a layer of an alloy of aluminum nitride (Al_zX_yN).

37. The method of claim 25, further comprising flip-chip mounting said first mirror layer, epitaxial semiconductor structure and substrate combination on a submount after depositing said first mirror, such that said first mirror layer is adjacent to said submount and said first mirror layer and epitaxial semiconductor structure is sandwiched between said submount and substrate.

38. The method of claim 37, wherein said submount comprises one of the group consisting of monocrystalline silicon carbide (SiC), a silicon substrate and glass.

39. A resonant cavity light emitting diode (RCLED), comprising:

a thin film epitaxial semiconductor structure;

a first mirror layer on one surface of said epitaxial semiconductor structure;

a second mirror layer on another surface of said epitaxial semiconductor structure such that said epitaxial semiconductor structure is sandwiched between said first and second mirrors, said second mirror layer being less reflective than said first mirror layer;

a submount, said epitaxial semiconductor structure with its said first and second mirrors mounted on said submount, said first mirror layer being adjacent to said submount and said second mirror layer being the primary emitting surface.

40. The RCLED of claim 39, wherein said epitaxial semiconductor device emits light and has a thickness to provide a resonant cavity for said light.

41. The RCLED of claim 39, wherein said epitaxial semiconductor device comprises two layers of semiconductor material that are oppositely doped.

42. The RCLED of claim 39, wherein said epitaxial semiconductor device comprises a semiconductor active region sandwiched between two oppositely doped layers.

43. The RCLED of claim 39, wherein said either said first or second mirror layer comprise a metal.

44. The RCLED of claim 39, wherein said first or second mirror layers comprise a distributed Bragg reflector (DBR).

45. A method for removing a silicon carbide substrate from a Group-III nitride epitaxial semiconductor material, comprising:

growing a Group-III nitride epitaxial semiconductor material on a silicon carbide substrate;

introducing an etch environment to said silicon carbide substrate, said etch environment etching silicon carbide faster than said Group-III nitride epitaxial material such that said etching substantially stops after said silicon carbide is etched off.

46. The method of claim 45, wherein said etch environment comprises a reactive ion etch.

47. The method of claim 45, wherein said etch environment comprises nitrogen trifluoride (NF₃) reactive ion etch.