UV light emitting devices and systems and methods for production
A method of fabricating an ultraviolet (UV) light emitting device includes receiving a UV transmissive substrate, forming a first UV transmissive layer comprising aluminum nitride upon the UV transmissive substrate using a first deposition technique at a temperature less than about 800 degrees Celsius or greater than about 1200 degrees Celsius, forming a second UV transmissive layer comprising aluminum nitride upon the first UV transmissive layer comprising aluminum nitride using a second deposition technique that is different from the first deposition technique, at a temperature within a range of about 800 degrees Celsius to about 1200 degrees Celsius, forming an n-type layer comprising aluminum gallium nitride layer upon the second UV transmissive layer, forming one or more quantum well structures comprising aluminum gallium nitride upon the n-type layer, and forming a p-type nitride layer upon the one or more quantum well structures.
1. An ultraviolet (UV) light emitting device comprising:
a UV transmissive substrate;
a first UV transmissive layer comprising polycrystalline aluminum nitride disposed upon the UV transmissive substrate, wherein the first UV transmissive layer is characterized by a first defect density;
a second UV transmissive layer comprising single crystal aluminum nitride disposed upon the first UV transmissive layer, wherein the second UV transmissive layer is characterized by a second defect density, and wherein the first defect density is higher than the second defect density;
an n-type layer comprising aluminum gallium nitride disposed upon the second UV transmissive layer;
one or more light emitting structures disposed upon the n-type layer; and
a p-type layer comprising nitride material disposed upon the one or more light emitting structures.
2. The UV device of claim 1 wherein the first UV transmissive layer and the second UV transmissive layer together have a thickness within a range within about 100 nm to about 3 microns.
3. The UV device of claim 1 wherein the first UV transmissive layer has a thickness different from a thickness of the second UV transmissive layer.
4. The UV device of claim 1 wherein the UV transmissive substrate has transmissivity in the UV wavelength range within a transmissivity range of about 50% to about 99%.
5. The UV device of claim 1 wherein the UV transmissive substrate comprises a plurality of patterns that scatter strongly with short wavelength UV light.
6. The UV device of claim 5 wherein the plurality of patterns comprises geometric features having a lateral spacing within a range of 0.1 to 5 microns.
7. The UV device of claim 1 wherein the one or more light emitting structures comprise structures selected from a group consisting of: quantum structures, and quantum wells.
8. The UV device of claim 1 , wherein the UV transmissive substrate is selected from a group consisting of: quartz, sapphire, and free standing single crystal aluminum nitride.
9. The UV device of claim 1 , wherein the first defect density is lower than 1e10 cm-2.
10. The UV device of claim 1 , wherein the first UV transmissive layer is also characterized by a contaminant density of less than 1e18 cm-3.
11. An ultraviolet (UV) light emitting device comprising:
a UV transmissive substrate;
a UV transmissive layer disposed upon the UV transmissive substrate, the UV transmissive layer comprising:
a first UV transmissive layer comprising a polycrystalline aluminum and nitrogen compound disposed upon the first UV transmissive substrate, wherein the first UV transmissive layer is characterized by a first quality;
a second UV transmissive layer comprising a single crystal aluminum and nitrogen compound disposed upon the first UV transmissive layer, wherein the second UV transmissive layer is characterized by a second quality, and wherein the first quality is lower than the second quality; and
a UV light emitting structure disposed upon the UV transmissive layer, the UV light emitting structure comprising:
an n-type layer comprising aluminum gallium nitride disposed upon the UV transmissive layer;
one or more light emitting structures disposed upon the n-type layer; and
a p-type layer comprising nitride material disposed upon the one or more light emitting structures.
12. The UV device of claim 11 wherein the UV transmissive layer has a thickness within a range within about 10 nm to about 3 microns.
13. The UV device of claim 11 wherein the UV transmissive layer has a thickness within a range within about 3 microns to about 10 microns.
14. The UV device of claim 11 wherein the UV transmissive layer has transmissivity in the UV wavelength range within a transmissivity range of about 50% to about 99%.
15. The UV device of claim 11
wherein the first quality comprises a first defect density;
wherein the second quality comprise a second defect density; and
wherein the second defect density is lower than the first defect density.
16. The UV device of claim 15 , wherein the first defect density is lower than 1e10 cm-2.
17. The UV device of claim 11 wherein the UV transmissive substrate comprises a plurality of patterns that scatter strongly with short wavelength UV light.
18. The UV device of claim 11 wherein the one or more light emitting structures comprise structures selected from a group consisting of: quantum structures, and quantum wells.
19. The UV device of claim 11 , wherein UV transmissive substrate is selected from a group consisting of: quartz, sapphire, and free standing single crystal aluminum nitride.
20. The UV device of claim 11 , wherein the first UV transmissive layer is also characterized by a contaminant density of less than 1e18 cm-3.