Granted Patent B2

US 7,582,498 · App. 11/295,627 · Granted Sep 1, 2009

Abstract

Claims (63)

1. A method for producing a resonant cavity light emitting device, the method comprising:

arranging a seed gallium nitride crystal and a source material in a nitrogen-containing superheated fluid in a container disposed in a multiple-zone furnace, the nitrogen-containing superheated fluid providing a medium for mass transport of gallium nitride precursors between the seed gallium nitride crystal and the source material, wherein the seed gallium nitride crystal has a dislocation density below 10 5 cm −2 and is substantially free of tilt boundaries,

preparing a surface of the seed gallium nitride crystal, comprising applying a first thermal profile between the seed gallium nitride crystal and the source material while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid, wherein the first thermal profile includes a first temperature gradient between the seed gallium nitride crystal and the source material;

growing gallium nitride material on the prepared surface of the seed gallium nitride crystal, the growing comprising applying a second thermal profile having a second temperature gradient that is different from the first temperature gradient between the seed gallium nitride crystal and the source material while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid, said growing producing a single-crystal gallium nitride substrate; and

depositing a stack of group III-nitride layers on the single-crystal gallium nitride substrate, the stack comprising a first mirror sub-stack and an active region adaptable for fabrication into one or more resonant cavity light emitting devices.

2. The method as defined in claim 1 , wherein the preparing of the surface of the seed gallium nitride crystal includes etching the seed gallium nitride crystal.

3. The method as defined in claim 2 , wherein:

the first thermal profile comprises a positive temperature gradient directed from the seed gallium nitride crystal toward the source material; and

the second thermal profile comprises a negative temperature gradient directed from the seed gallium nitride crystal toward the source material.

4. The method as defined in claim 1 , wherein the preparing of the surface of the seed gallium nitride crystal further comprises: applying the first thermal

profile to effect a growing of gallium nitride crystal on the seed gallium nitride crystal at a growth rate that is slower than a growth rate effected by the applying of the second thermal profile.

5. The method as defined in claim 1 , further comprising transitioning from the first thermal profile to the second thermal profile over a determined time interval to produce an increasing growth rate of gallium nitride on the seed gallium nitride crystal over the time interval.

6. The method as defined in claim 1 , wherein the first thermal profile and the second thermal profile have temperature gradients of opposing direction.

7. The method as defined in claim 1 , wherein the container is fabricated from at least one material selected from the group consisting of copper, gold, silver, palladium, platinum, iridium, ruthenium rhodium, osmium, niobium, molybdenum, tantalum, tungsten, rhenium and nickel alloy.

8. The method as defined in claim 7 , wherein:

a temperature differential of the seed gallium nitride crystal and the source material is larger in the second thermal profile than a temperature differential in the first thermal profile.

9. The method as defined in claim 7 , further comprising arranging an ammonium chloride mineralizer and/or an ammonium fluoride mineralizer in the nitrogen-containing superheated fluid for promoting dissolving of gallium nitride into the nitrogen-containing superheated fluid during the preparing and growing, wherein the second thermal profile has a temperature gradient chosen so that etching of the source material and growth on the seed gallium nitride takes place.

10. The method as defined in claim 7 , further comprising arranging an ammonium fluoride mineralizer in the nitrogen-containing superheated fluid, the mineralizer being capable of facilitating dissolution of gallium nitride into the nitrogen-containing superheated fluid.

11. The method as defined in claim 1 , further comprising arranging a luminescent dopant comprising at least one of a transition metal and a rare earth metal in one of the nitrogen-containing superheated fluid and the gallium nitride source material.

12. The method as defined in claim 1 , further comprising subsequent to the depositing of the stack, fabricating a plurality of resonant cavity light emitting devices thereon.

13. The method as defined in claim 12 , further comprising dicing the single-crystal gallium nitride substrate to separate the plurality of resonant cavity light emitting devices from each other.

14. The method as defined in claim 1 , further comprising, prior to the depositing of the stack, slicing the single-crystal gallium nitride substrate into a plurality of about planar wafers, wherein the depositing of the stack includes depositing the stack on at least one of the plurality of wafers.

15. The method as defined in claim 14 , wherein the slicing produces a plurality of about planar (0001) oriented wafers each having (0001) and (0001) oriented surfaces on opposing sides of the wafer, the method further comprising:

polishing one of the (0001) oriented surface and the (0001) oriented surface of a selected (0001) oriented wafer, the stack being deposited on the polished surface.

16. The method as defined in claim 14 , wherein the slicing produces a plurality of about planar (1100) oriented wafers.

17. The method as defined in claim 14 , wherein the slicing produces a plurality of about planar (1120) oriented wafers.

18. The method as defined in claim 1 , wherein the superheated fluid is at a determined temperature and pressure such that the superheated fluid is supercritical.

19. A method, comprising:

arranging a seed gallium nitride crystal and a source material in a nitrogen-containing superheated fluid disposed in a sealable container disposed in a multiple-zone furnace;

growing gallium nitride material on the seed gallium nitride crystal by mass transport from the source material to the seed gallium nitride crystal through the nitrogen-containing superheated fluid, said growing producing a single-crystal gallium nitride substrate secured to the seed gallium nitride crystal, said growing comprising applying a temporally varying thermal gradient between the seed gallium nitride crystal and the source material to produce an increasing growth rate during at least a portion of the growing; and

depositing a stack of group III-nitride layers on the single-crystal gallium nitride substrate, the stack comprising a first mirror sub-stack and an active region adaptable for fabrication into one or more resonant cavity light emitting devices.

20. The method as defined in claim 19 , wherein the applying of a temporally varying thermal gradient to produce an increasing growth rate during at least a portion of the growing includes:

reversing a direction of the thermal gradient during the temporal varying.

21. The method as defined in claim 19 , wherein the depositing of the stack of group III-nitride layers on the single-crystal gallium nitride substrate includes:

depositing the stack of group III-nitride layers by one of metal-organic chemical vapor deposition and molecular beam epitaxy.

22. The method as defined in claim 19 , further comprising:

slicing the single-crystal gallium nitride substrate into a plurality of wafers; and

polishing a surface of a selected wafer, the depositing of the stack of group III-nitride layers being performed on the polished surface of the selected wafer.

23. The method as defined in claim 19 , wherein the depositing of the stack of group III-nitride layers on the single-crystal gallium nitride substrate includes:

depositing a second mirror sub-stack, the first mirror sub-stack and the second mirror sub-stack defining a resonant cavity surrounding the active region.

24. The method as defined in claim 19 , further comprising:

depositing a reflector of a material other than a group III-nitride material on the stack, the first mirror sub-stack and the reflector defining a resonant cavity surrounding the active region.

25. The method as defined in claim 19 , further comprising:

processing the stack of group III-nitride layers to define a plurality of light emitting devices secured to the single-crystal gallium nitride substrate, the plurality of light emitting devices being selected from a group consisting of a plurality of resonant cavity light emitting diodes and a plurality of vertical cavity surface emitting lasers.

26. A system for producing a resonant cavity light emitting device, comprising

means for arranging a seed gallium nitride crystal and a source material in a nitrogen-containing superheated fluid in a container disposed in a multiple-zone furnace, the nitrogen-containing superheated fluid providing a medium for mass transport of gallium nitride precursors between the seed gallium nitride crystal and the source material;

means for applying a first thermal profile between the seed gallium nitride crystal and the source material while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid to prepare a surface of the seed gallium nitride crystal;

means for growing gallium nitride material on the prepared surface of the seed gallium nitride crystal, the growing comprising applying a second thermal profile that is different from the first thermal profile between the seed gallium nitride crystal and the source material while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid, said growing producing a single-crystal gallium nitride substrate; and

means for depositing a stack of group III-nitride layers on the single-crystal gallium nitride substrate, the stack comprising a first mirror sub-stack and an active region adaptable for fabrication into one or more resonant cavity light emitting devices.

27. A method for producing a resonant cavity light emitting device, the method comprising:

a) arranging a seed gallium nitride crystal and a source material in a nitrogen-containing superheated fluid in a container disposed in a multiple-zone furnace, the nitrogen-containing superheated fluid providing a medium for mass transport of gallium nitride precursors between the seed gallium nitride crystal and the source material;

b) etching a surface of the seed gallium nitride crystal; then

c) growing gallium nitride material on the etched surface of the seed gallium nitride crystal, said growing producing a single-crystal gallium nitride substrate; and

d) depositing a stack of group III-nitride layers on the single-crystal gallium nitride substrate, the stack comprising a first mirror sub-stack and an active region adaptable for fabrication into one or more resonant cavity light emitting devices.

28. The method of claim 27 wherein the step (b) of etching the surface of the seed gallium nitride crystal comprises applying a first thermal profile between the seed gallium nitride crystal and the source material while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid wherein the temperature of the seed gallium nitride crystal is lower than the temperature of the source material.

29. The method of claim 28 wherein the step (c) of growing the gallium nitride material on the etched surface of the seed gallium nitride crystal comprises applying a second thermal profile while the seed gallium nitride crystal and the source material are arranged in the nitrogen-containing superheated fluid, wherein the temperature of the seed gallium nitride crystal is higher than the temperature of the source material.

30. A method for producing a resonant cavity light emitting device, the method comprising:

arranging a seed gallium nitride crystal and a source material in a nitrogen-containing superheated fluid in a container disposed in a multiple-zone furnace, the nitrogen-containing superheated fluid providing a medium for mass transport of gallium nitride precursors between the seed gallium nitride crystal and the source material, wherein the seed gallium nitride crystal has a dislocation density below 10 5 cm −2 ;

further providing a halide salt mineralizer comprising at least one NH 4 F and NH 4 Cl in the nitrogen-containing superheated fluid for promoting dissolving of gallium nitride into the nitrogen-containing superheated fluid;

growing gallium nitride material on the surface of the seed gallium nitride crystal, said growing producing a single-crystal gallium nitride boule; and

depositing a stack of group III-nitride layers on a single-crystal gallium nitride wafer, said wafer having been prepared from the single-crystal gallium nitride boule, the stack comprising a first mirror sub-stack and an active region adaptable for fabrication into one or more resonant cavity light emitting devices.

31. The method as defined in claim 30 , further comprising arranging a luminescent dopant comprising at least one of a transition metal and a rare earth metal in one of the nitrogen-containing superheated fluid and the gallium nitride source material.

32. The method as defined in claim 30 , further comprising subsequent to the depositing of the stack, fabricating a plurality of resonant cavity light emitting devices thereon.

Assignments (15)