Methods of fabricating micro- and nanostructure arrays and structures formed therefrom
Methods of fabricating micro- and nanostructures comprise top-down etching of lithographically patterned GaN layer to form an array of micro- or nanopillar structures, followed by selective growth of GaN shells over the pillar structures via selective epitaxy. Also provided are methods of forming micro- and nanodisk structures and microstructures formed from thereby.
1. A method of fabricating an array of microstructures, comprising the steps of:
providing an epilayer of gallium nitride (GaN) grown on a substrate;
etching an array of GaN pillars in said epilayer; and
growing GaN shells on said etched array of GaN pillars to form core-shell structures via selective epitaxy, wherein a first portion of said GaN shells are doped with a first material, and a second portion of said GaN shells are doped with a second material different than said first material.
2. The method of claim 1 , wherein said substrate comprises a material selected from the group consisting of sapphire, silicon, gallium arsenide, and silicon carbide.
3. The method of claim 1 , wherein said substrate further comprises a buffer layer intermediate a base layer and said GaN epilayer.
4. The method of claim 3 , wherein said buffer layer comprises at least one of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN).
5. The method of claim 1 , wherein a least a portion of said GaN pillars are doped with silicon, magnesium, zinc, or iron.
6. The method of claim 1 , wherein at least a portion of said GaN shells are doped with silicon, magnesium, zinc, or iron.
7. The method of claim 1 , wherein said first portion of said GaN shells have a first chemical composition, and said second portion of said GaN shells have a second chemical composition different than said first chemical composition.
8. The method of claim 7 , wherein said first and second portions of said GaN shells are sequentially grown on said etched array of GaN pillars.
9. The method of claim 1 , wherein said etching step comprises inductively coupled plasma (ICP) etching.
10. The method of claim 9 , comprising the further step of chemically etching said ICP etched array of pillars.
11. The method of claim 10 , wherein said chemically etching step comprises hot phosphoric acid etching.
12. The method of claim 10 , wherein said chemically etching step comprises etching in a solution comprising potassium hydroxide (KOH).
13. The method of claim 1 , wherein said selective epitaxy is hydride vapor phase epitaxy (HVPE).
14. The method of claim 13 , wherein said HVPE utilizes at least one of ammonia, nitrogen, or hydrogen chloride gas.
15. The method of claim 13 , wherein said HVPE is conducted at a temperature of between about 850° C. and about 1150° C.
16. The method of claim 13 , wherein said HVPE is conducted at a pressure between about 10 Torr and about 760 Torr.
17. The method of claim 1 , wherein said core-shell structures have inclined {1-101} sidewalls.
18. The method of claim 1 , wherein said core-shell structures have vertical {1-100} sidewalls.