Miscut bulk substrates
View Patent ↗A method for providing (Al,Ga,In)N thin films on Ga-face c-plane (Al,Ga,In)N substrates using c-plane surfaces with a miscut greater than at least 0.35 degrees toward the m-direction. Light emitting devices are formed on the smooth (Al,Ga,In)N thin films. Devices fabricated on the smooth surfaces exhibit improved performance.
1. A device comprising;
a bulk (Al,Ga,In)N substrate;
a plurality of epitaxial layers overlying the bulk (Al,Ga,In)N substrate and defining a light-emitting device structure,
wherein a top surface of the device structure is characterized by a nominal c-plane crystallographic orientation miscut by an angle from 0.35 degrees to 1 degrees toward an m-direction; and
wherein the epitaxial layers of the light-emitting device structure are configured to have a standard deviation of photoluminescent wavelength uniformity of less than 1% over at least a 2,500 μm 2 area.
2. The device of claim 1 , wherein:
the epitaxial layers of the light-emitting device structure are configured such that the top first surface is characterized by a root mean square surface roughness of less than 1 nm over the at least 2,500 μm 2 surface area.
3. The device of claim 2 , comprising at least one n-type doped layer overlying the bulk (Al,Ga,In)N substrate.
4. The device of claim 3 , comprising at least one active region overlying the at least one n-type doped layer.
5. The device of claim 4 , wherein the top surface is characterized by a nominal Ga-face c-plane crystallographic orientation miscut by an angle from 0.35 degrees to 1 degrees toward a <1-100> direction, and by an angle from −1 degree to 1 degree toward a <11-20> direction.
6. The device of claim 4 , comprising at least one p-type doped layer overlying the at least one active region.
7. The device of claim 4 , wherein the at least one active layer comprises AlInGaN.
8. The device of claim 1 , wherein the top surface is characterized by an RMS surface roughness from 0.25 nm to 0.6 nm over at least a 2,500 μm 2 surface area.
9. The device of claim 1 , wherein the top surface is characterized by a RMS surface roughness less than 0.2 nm over at least a 2,500 μm 2 area.
10. The device of claim 1 , wherein the device structure is characterized by a standard deviation of photoluminescent wavelength uniformity is less than 1% over at least a 2,500 μm 2 surface area.
11. The device of claim 1 , wherein the device structure is characterized by a standard deviation of photoluminescent wavelength uniformity is less than 0.2% over at least a 2,500 μm 2 surface area.
12. The device of claim 1 , wherein the miscut angle is from 0.35 degrees to 0.8 degrees toward the m-direction.
13. The device of claim 1 , wherein the top surface is further characterized by a miscut angle from −1 degrees to 1 degree toward a <11-20> direction.
14. The device of claim 1 , wherein the device comprises a light emitting diode.
15. The device of claim 14 , wherein the light emitting diode is characterized by an output power of at least 2 milliwatts at 20 milliamps drive current.
16. The device of claim 1 , wherein the bulk (Al,Ga,In)N is bulk GaN.
17. The device of claim 1 , wherein the device comprises a wafer.
18. A semiconductor device fabricated from the wafer of claim 17 .