Large Area, Low-Defect Gallium-Containing Nitride Crystals, Method of Making, and Method of Use

• US 20140065360A1
• Filed: 08/30/2012
• Published: 03/06/2014
• Est. Priority Date: 07/07/2008
• Status: Active Grant

• Current Assignee: SL Technology Incorporated (Reliv' International, Inc.)
• Original Assignee: Soraa, Inc.
• Inventors: D'Evelyn, Mark P., Ehrentaut, Dirk, Jiang, Wenkan, Downey, Bradley C.
• Granted Patent: US 9,404,197 B2
• Time in Patent Office: Days
• US Class Current: 428/141
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 25/20 the substrate being of the same materials as the epitaxial layer
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: C30B 33/06 Joining of crystals
• CPC Class Codes: C30B 7/105 using ammonia as solvent, i.e. ammonothermal processes
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 31/03044 comprising a nitride compounds, e.g. GaN
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 2304/00 Special growth methods for semiconductor lasers
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]

Abstract

An ultralow defect gallium-containing nitride crystal and methods of making ultralow defect gallium-containing nitride crystals are disclosed. The crystals are useful as substrates for light emitting diodes, laser diodes, transistors, photodetectors, solar cells, and photoelectrochemical water splitting for hydrogen generators.

Claims

1. An ultralow defect gallium-containing nitride crystal, wherein:

the crystal comprises gallium and nitrogen and has a wurtzite crystal structure;

the crystal comprises a first large area surface and a second large area surface, the second large area surface being on the opposite side of the crystal, and the first large area surface and the second large area surface being substantially parallel to one another and having a maximum dimension greater than about 10 millimeters;

wherein

the first large-area surface comprises a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

60 degrees and about +60 degrees toward a [0001] +c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction; and

at least one of the first large area surface and the second large area surface is characterized by a dislocation density below about 10⁴ cm<sup>−

2</sup> and by a stacking fault concentration below about 10 cm<sup>−

1</sup>, as determined by etching, in a solution comprising one or more of H₃PO₄, H₃PO₄ that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H₂SO₄, at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours;

wherein the temperature and the time are selected so as to cause formation of etch pits with diameters between about 1 micrometer and about 25 micrometers.

2. The crystal of claim 1, wherein the second large-area surface comprises a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

60 degrees and about +60 degrees toward a [0001] +c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction; and

3. The crystal of claim 1, wherein one of the first large area surface and the second large area surface are polished before the etching.

4. The crystal of claim 1, wherein both the first large area surface and the second large area surface are polished before the etching.

5. The crystal of claim 1, wherein the crystallographic orientation of the first large-area surface has a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

30 degrees and about +30 degrees toward a [0001] +c-direction and by up to about 5 degrees toward an orthogonal <

1-210>

a-direction.

6. The crystal of claim 1, wherein the crystallographic orientation of the first large-area surface is miscut from a {10-10} m-plane by between about −

5 degrees and about +5 degrees toward a [0001] +c-direction and by up to about 1 degree toward an orthogonal <

1-210>

a-direction.

7. The crystal of claim 1, wherein the crystallographic orientation of the first large-area surface is within about 5 degrees of a semipolar orientation selected from a {60-6±

1} plane, a {50-5±

1} plane, a {40-4±

1} plane, a {30-3±

1} plane, a {50-5±

2} plane, a {70-7±

3} plane, a {20-2±

1} plane, a {30-3±

2} plane, a {40-4±

3} plane, a {50-5±

4} plane, a {10-1±

1} plane, a {1 0 −

1 ±

2} plane, and a {1 0 −

1 ±

3} plane.

8. The crystal of claim 1, wherein the first large-area surface is characterized by an impurity concentration of oxygen (O) between about 1×

10¹⁶ cm<sup>−

3</sup> and 1×

10¹⁹ cm<sup>−

3</sup>;

an impurity concentration of hydrogen (H) between about 1×

10¹⁶ cm<sup>−

3</sup> and 2×

10¹⁹ cm<sup>−

3</sup>; and

an impurity concentration of at least one of fluorine (F) and chlorine (Cl) between about 1×

10¹⁵ cm<sup>−

3</sup> and 1×

10¹⁷ cm<sup>−

3</sup>.

9. The crystal of claim 1, wherein the first large-area surface is characterized by an impurity concentration of oxygen (O) between about 1×

10¹⁶ cm<sup>−

3</sup> and 1×

10¹⁹ cm<sup>−

3</sup>;

an impurity concentration of hydrogen (H) between about 1×

10¹⁶ cm<sup>−

3</sup> and 2×

10¹⁹ cm<sup>−

3</sup>; and

an impurity concentration of at least one of sodium (Na) and potassium (K) between about 3×

10¹⁵ cm<sup>−

3</sup> and 1×

10¹⁸ cm<sup>−

3</sup>.

10. The crystal of claim 1, further comprising at least two single crystal domains having a gallium-containing nitride composition, wherein the at least two single crystal domains comprise a dislocation density within the domain less than about 10⁴ cm⁻

2, are separated by a line of dislocations with a linear density than about 1×

10⁵ cm<sup>−

1</sup>, a polar misorientation angle γ

between the first domain and the second domain is between about 0.01 degree and about 0.5 degree, and azimuthal misorientation angles α and

β

are between about 0.01 degree and about 1 degree.

11. The crystal of claim 1, wherein the crystal comprises a substantially wurtzite structure that is substantially free of other crystal structures, the other crystal structures being less than about 1% in volume than a volume of the substantially wurtzite structure.

12. The crystal of claim 1, wherein the first large-area surface comprises a root-mean-square surface roughness measured over a 10-micrometer by 10-micrometer area that is less than about 1 nanometer.

13. The crystal of claim 1, wherein at least one of the first large area surface and the second large area surface is characterized by a dislocation density below about 10³ cm⁻

2 and by a stacking fault concentration below about 1 cm<sup>−

1</sup>.

14. The crystal of claim 1, further comprising a semiconductor structure fabricated on the first large area surface, the semiconductor structure comprising at least one Al_xIn_yGa_(1-x-y)N epitaxial layer, wherein 0≦

x, y, x+y≦

1.

15. An ultralow defect gallium-containing nitride crystal, wherein:

the crystal comprises gallium and nitrogen and has a wurtzite crystal structure;

the crystal comprises a first large area surface and a second large area surface, the second large area surface being on the opposite side of the crystal, the first large area surface and the second large area surface being substantially parallel to one another and having a maximum dimension greater than about 10 millimeters;

wherein

the first large-area surface comprises a crystallographic orientation within 5 degrees of an orientation selected from a (0001) +c-plane and a (000-1) −

c-plane;

the large-area surface closest in orientation to a (0001) plane is characterized by a dislocation density below about 10⁴ cm<sup>−

2</sup>, as determined by a first etching process in a melt comprising at least one of NaOH and KOH at a temperature between about 300 degrees Celsius and about 500 degrees Celsius for a time between about 30 seconds and about one hour, wherein the time and the temperature of the first etching process are selected so as to cause formation of c-plane etch pits with diameters between about 1 micrometer and about 25 micrometers; and

an m-plane surface comprising a surface area of at least about 3 square millimeters characterized by a dislocation density below about 10⁴ cm<sup>−

2</sup> and is free of stacking faults, as determined by a second etching process comprising etching in a solution comprising one or more of H₃PO₄, H₃PO₄ that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H₂SO₄, at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for a time between about 5 minutes and about 5 hours;

wherein the temperature and the time of the second etching process are selected so as to cause formation of m-plane etch pits with diameters between about 1 micrometer and about 25 micrometers, and the (000-1) −

c surface is protected by contact with an etch-resistant material during the second etching process.

16. The crystal of claim 15, wherein the second large-area surface comprises a crystallographic orientation that is miscut from a {10-10} m-plane by between about −

60 degrees and about +60 degrees toward a [0001] +c-direction and by up to about 10 degrees toward an orthogonal <

1-210>

a-direction; and

17. The crystal of claim 15, wherein one of the first large area surface and the second large area surface are polished before the etching.

18. The crystal of claim 15, wherein both the first large area surface and the second large area surface are polished before the etching.

19. The crystal of claim 15, wherein the first large-area surface is characterized by an impurity concentration of oxygen (O) between about 1×

10¹⁶ cm<sup>−

3</sup> and 1×

10¹⁹ cm<sup>−

3</sup>;

an impurity concentration of hydrogen (H) between about 1×

10¹⁶ cm<sup>−

3</sup> and 2×

10¹⁹ cm<sup>−

3</sup>; and

an impurity concentration of at least one of fluorine (F) and chlorine (Cl) between about 1×

10¹⁵ cm<sup>−

3</sup> and 1×

10¹⁷ cm<sup>−

3</sup>.

20. The crystal of claim 15, wherein the first large-area surface is characterized by an impurity concentration of oxygen (O) between about 1×

10¹⁶ cm<sup>−

3</sup> and 1×

10¹⁹ cm<sup>−

3</sup>;

an impurity concentration of hydrogen (H) between about 1×

10¹⁶ cm<sup>−

3</sup> and 2×

10¹⁹ cm<sup>−

3</sup>, and an impurity concentration of at least one of sodium (Na) and potassium (K) between about 3×

10¹⁵ cm<sup>−

3</sup> and 1×

10¹⁸ cm<sup>−

3</sup>.

21. The crystal of claim 15, further comprising at least two single crystal domains having a gallium-containing nitride composition, wherein the at least two single crystal domains comprise a dislocation density within the domain less than about 10⁴ cm⁻

2, are separated by a line of dislocations with a linear density than about 1×

10⁵ cm<sup>−

1</sup>, a polar misorientation angle γ

between the first domain and the second domain is between about 0.01 degree and about 0.5 degree, and azimuthal misorientation angles α and

β

are between about 0.01 degree and about 1 degree.

22. The crystal of claim 15, wherein the crystal comprises a substantially wurtzite structure that is substantially free of other crystal structures, the other crystal structures being less than about 1% in volume than a volume of the substantially wurtzite structure.

23. The crystal of claim 15, wherein the first large-area surface comprises a root-mean-square surface roughness measured over a 10-micrometer by 10-micrometer area that is less than about 1 nanometer.

24. The crystal of claim 15, further comprising a semiconductor structure fabricated on the first large area surface, the semiconductor structure comprising at least one Al_xIn_yGa_(1-x-y)N epitaxial layer, wherein 0≦

x, y, x+y≦

1.