Transparent group III metal nitride and method of manufacture
Large-area, low-cost single crystal transparent gallium-containing nitride crystals useful as substrates for fabricating GaN devices for electronic and/or optoelectronic applications are disclosed. The gallium-containing nitride crystals are formed by controlling impurity concentrations during ammonothermal growth and processing to control the relative concentrations of point defect species.
1. A gallium-containing nitride crystal comprising:
a top surface having a crystallographic orientation within about 5 degrees of a plane selected from a (0001)+c-plane and a (000-1)−c-plane;
a substantially wurtzite structure;
n-type electronic properties;
an impurity concentration greater than about 2×10 17 cm −3 of hydrogen;
an impurity concentration less than about 1×10 17 cm −3 of oxygen;
an H/O ratio of at least 10;
an impurity concentration greater than about 2×10 14 cm −3 of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl;
an optical absorption coefficient less than about 5 cm −1 at a wavelength of 400 nanometers;
an optical absorption coefficient less than about 4 cm −1 at a wavelength of 410 nanometers;
an optical absorption coefficient less than about 3 cm −1 at a wavelength of 415 nanometers; and
an optical absorption coefficient less than about 2 cm −1 at a wavelength of 450 nanometers;
wherein the gallium-containing nitride crystal is characterized by,
an absorbance per unit thickness of at least 0.01 cm −1 at wavenumbers of 3218 cm −1 , 3202 cm −1 , and 3188 cm −1 ; and
no infrared absorption peaks at wavenumbers between about 3175 cm −1 and about 3000 cm −1 having an absorbance per unit thickness greater than 10% of the absorbance per unit thickness at 3218 cm −1 .
2. The gallium-containing nitride crystal of claim 1 , characterized by a carrier concentration n between about 10 16 cm −3 and 10 20 cm −3 and a carrier mobility η, in units of centimeters squared per volt-second, such that the logarithm to the base 10 of η is greater than −0.018557[log 10 (n)] 3 +1.0671[log 10 (n)] 2 −20.599[log 10 (n)]+135.49.
3. The gallium-containing nitride crystal of claim 1 , further comprising an impurity concentration of at least one of silicon and germanium between about 1×10 17 cm −3 and about 3×10 18 cm −3 .
4. The gallium-containing nitride crystal of claim 1 , wherein the carrier concentration is between about 3×10 17 cm −3 and about 3×10 18 cm −3 .
5. The gallium-containing nitride crystal of claim 1 , wherein the top surface has a diameter greater than about 10 millimeters and the crystal has a thickness greater than about 100 micrometers.
6. The gallium-containing nitride crystal of claim 1 , comprising an impurity concentration of at least one of F and Cl between about 2×10 14 cm −3 and about 5×10 17 cm −3 .
7. A device comprising the gallium-containing nitride crystal of claim 1 .
8. A gallium-containing nitride crystal comprising:
a top surface having a crystallographic orientation within about 5 degrees of a plane selected from a (0001)+c-plane and a (000-1)−c-plane;
a substantially wurtzite structure;
n-type electronic properties;
an impurity concentration greater than about 5×10 17 cm −3 of hydrogen;
an impurity concentration between about 2×10 17 cm −3 and about 4×10 18 cm −3 of oxygen;
an H/O ratio of at least 0.3;
an impurity concentration greater than about 1×10 16 cm −3 of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl;
an optical absorption coefficient less than about 8 cm −1 at a wavelength of 400 nanometers;
an optical absorption coefficient less than about 6 cm −1 at a wavelength of 410 nanometers;
an optical absorption coefficient less than about 5.5 cm −1 at a wavelength of 415 nanometers;
an optical absorption coefficient less than about 4 cm −1 at a wavelength of 450 nanometers;
an absorbance per unit thickness of at least 0.01 cm −1 at wavenumbers of approximately 3175 cm −1 , 3164 cm −1 , and 3150 cm −1 ;
no infrared absorption peaks at wavenumbers between about 3200 cm −1 and about 3400 cm −1 or between about 3075 cm −1 and about 3125 cm −1 having an absorbance per unit thickness greater than 10% of the absorbance per unit thickness at 3175 cm −1 .
9. The gallium-containing nitride crystal of claim 8 , characterized by a carrier concentration n between about 10 16 cm −3 and 10 20 cm −3 and a carrier mobility η, in units of centimeters squared per volt-second, such that the logarithm to the base 10 of η is greater than −0.018557[log 10 (n)] 3 +1.0671[log 10 (n)] 2 −20.599[log 10 (n)]+135.49.
10. The gallium-containing nitride crystal of claim 8 , further comprising an impurity concentration of at least one of silicon and germanium between about 1×10 17 cm −3 and about 3×10 18 cm −3 .
11. The gallium-containing nitride crystal of claim 8 , wherein the carrier concentration is between about 3×10 17 cm −3 and about 3×10 18 cm −3 .
12. The gallium-containing nitride crystal of claim 8 , wherein the top surface has a diameter greater than about 10 millimeters and the crystal has a thickness greater than about 100 micrometers.
13. The gallium-containing nitride crystal of claim 8 , characterized by,
an optical absorption coefficient less than about 4 cm −1 at a wavelength of 400 nanometers;
an optical absorption coefficient less than about 3 cm −1 at a wavelength of 410 nanometers;
an optical absorption coefficient less than about 2.5 cm −1 at a wavelength of 415 nanometers; and
an optical absorption coefficient less than about 1.5 cm −1 at a wavelength of 450 nanometers.
14. The gallium-containing nitride crystal of claim 8 , characterized by,
an optical absorption coefficient less than about 3 cm −1 at a wavelength of 400 nanometers;
an optical absorption coefficient less than about 2.2 cm −1 at a wavelength of 410 nanometers;
an optical absorption coefficient less than about 2.0 cm −1 at a wavelength of 415 nanometers; and
an optical absorption coefficient less than about 1.0 cm −1 at a wavelength of 450 nanometers.
15. A device comprising the gallium-containing nitride crystal of claim 8 .
16. A gallium-containing nitride crystal comprising:
a top surface having a crystallographic orientation within about 5 degrees of a {1 0-1 0} m-plane;
a substantially wurtzite structure;
n-type electronic properties;
an impurity concentration greater than about 3×10 18 cm −3 of hydrogen;
an impurity concentration between about 5×10 17 cm −3 and about 3×10 19 cm −3 of oxygen;
an H/O ratio of at least 1.1;
an impurity concentration greater than about 1×10 16 cm −3 of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl;
an optical absorption coefficient less than about 8 cm −1 at a wavelength of 400 nanometers;
an optical absorption coefficient less than about 6 cm −1 at a wavelength of 410 nanometers;
an optical absorption coefficient less than about 5.5 cm −1 at a wavelength of 415 nanometers;
an optical absorption coefficient less than about 4 cm −1 at a wavelength of 450 nanometers;
an absorbance per unit thickness of at least 0.01 cm −1 at 3188 cm −1 , 3175 cm −1 , 3164 cm −1 , and 3150 cm −1 ; and
no infrared absorption peaks at wavenumbers between about 3125 cm −1 and about 3000 cm −1 , having an absorbance per unit thickness greater than 10% of the absorbance per unit thickness at 3188 cm −1 .
17. The gallium-containing nitride crystal of claim 16 , characterized by a carrier concentration n between about 10 16 cm −3 and 10 20 cm −3 and a carrier mobility η, in units of centimeters squared per volt-second, such that the logarithm to the base 10 of η is greater than −0.018557[log 10 (n)] 3 +1.0671[log 10 (n)] 2 −20.599[log 10 (n)]+135.49.
18. The gallium-containing nitride crystal of claim 16 , wherein the absorbance per unit thickness at 3232 cm −1 is at least 0.01 cm −1 .
19. The gallium-containing nitride crystal of claim 16 , further comprising an impurity concentration of at least one of silicon and germanium between about 1×10 17 cm −3 and about 3×10 18 cm −3 .
20. The gallium-containing nitride crystal of claim 16 , wherein the carrier concentration is between about 3×10 17 cm −3 and about 3×10 18 cm −3 .
21. The gallium-containing nitride crystal of claim 16 , wherein the top surface has a diameter greater than about 10 millimeters and the crystal has a thickness greater than about 100 micrometers.
22. A device comprising the gallium-containing nitride crystal of claim 16 .