Group III-nitride layers with patterned surfaces
A fabrication method produces a mechanically patterned layer of group III-nitride. The method includes providing a crystalline substrate and forming a first layer of a first group III-nitride on a planar surface of the substrate. The first layer has a single polarity and also has a pattern of holes or trenches that expose a portion of the substrate. The method includes then, epitaxially growing a second layer of a second group III-nitride over the first layer and the exposed portion of substrate. The first and second group III-nitrides have different alloy compositions. The method also includes subjecting the second layer to an aqueous solution of base to mechanically pattern the second layer.
1. A method of fabricating a structure, comprising:
providing a substrate with a planar surface;
providing a crystalline layer of a group III-nitride over the surface of the substrate; and
subjecting the layer to base to etch a top surface of the layer such that a plurality of pyramids are formed from nitrogen-polarity first lateral regions of the layer and pyramids are not formed in an adjacent second lateral region of the layer, the second lateral region being located between the first lateral regions; and
wherein the structure has a metallic electrode located on a flat surface of the second lateral region of the layer.
2. The method of claim 1 , wherein the subjecting forms the pyramids by etching a portion of the top surface of the layer having metal-polarity.
3. The method of claim 1 , wherein the subjecting does not significantly etch a portion of the top surface of the layer that has metal-polarity.
4. The method of claim 3 , wherein the subjecting forms the pyramids by etching a portion of the top surface of the layer that has metal-polarity.
5. The method of claim 1 , wherein the group III-nitride comprises gallium.
6. The method of claim 1 , wherein the layer is an epitaxially grown layer.
7. The method of claim 1 , wherein the layer comprises a gallium nitride layer.
8. The method of claim 1 , wherein the pyramids spatially overlap.
9. The method of claim 1 , wherein tips of the pyramids have an irregular spatial distribution.
10. The method of claim 1 , wherein the pyramids are physically separated from any electrode.
11. The method of claim 1 , wherein the electrode is located on a flat portion of the top surface.
12. The method of claim 1 , wherein a portion of the layer of the group III-nitride is located on the layer of another group III-nitride alloy.
13. The method of claim 1 , wherein the base is aqueous base.
14. The method of claim 13 , wherein the subjecting does not significantly etch a portion of the top surface of the layer that has metal-polarity.
15. The method of claim 13 , wherein the layer is an epitaxially grown layer.
16. The method of claim 13 , wherein the layer comprises gallium nitride.
17. The method of claim 13 , wherein the pyramids spatially overlap.
18. The method of claim 13 , wherein tips of the pyramids have an irregular spatial distribution.
19. The method of claim 13 , further comprising providing a metal electrode on a portion of a surface of the layer.
20. The method of claim 13 , wherein the pyramids are physically separated from any electrode.
21. The method of claim 13 , wherein the electrode is located on a flat portion of the top surface.
22. An apparatus, comprising:
a layer of group III-nitride having a top surface, the top surface having a plurality of pyramidal structures of the group III-nitride;
a metallic electrode located directly on a flat surface of the layer between portions of the layer having the pyramidal structures, the pyramidal structures of the top surface being physically separated from the electrode; and
a phosphor screen facing the top surface.
23. The apparatus of claim 22, wherein the pyramidal structures are located on a part of the top surface having nitrogen-polarity.
24. The apparatus of claim 22, wherein the group III-nitride comprises gallium.
25. The apparatus of claim 22, wherein the pyramidal structures spatially overlap.
26. The apparatus of claim 23, wherein the group III-nitride comprises gallium.
27. The apparatus of claim 23, wherein the pyramidal structures spatially overlap.
28. The apparatus of claim 22, wherein the pyramidal structures have a random distribution.