Nanowire-templated lateral epitaxial growth of non-polar group III nitrides
View Patent ↗A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.
1. A method for nanowire-templated lateral epitaxial growth of nonpolar Group III nitrides, comprising:
forming a plurality of metal catalyst nanoclusters on a surface of a crystallographic template substrate;
growing by a metal-organic chemical vapor growth technique a plurality of single-crystal Group III nitride nanowires that are substantially vertically oriented relative to the surface using the plurality of metal catalyst nanoclusters to catalyze nanowire growth under nanowire growth conditions, wherein the single-crystal Group III nitride nanowires are crystallographically aligned with the crystallographic template substrate; and
growing by a metal-organic chemical vapor growth technique a Group III nitride material laterally from the single-crystal Group III nitride nanowires under lateral growth conditions to form a coalesced Group III nitride layer.
2. The method of claim 1 , wherein the crystallographic template substrate is r-plane sapphire or a-plane GaN.
3. The method of claim 1 , wherein the nanowire growth conditions and the lateral growth conditions comprise a Group III metal precursor and a nitrogen precursor, and wherein a ratio of nitrogen precursor to Group III metal precursor is greater than 1.
4. The method of claim 3 , wherein the Group III metal precursor is selected from the group consisting of trimethyl gallium, triethyl gallium, gallium-containing hydrocarbon compounds, gallium oxide, and gallium nitride.
5. The method of claim 3 , wherein the nitrogen precursor is selected from the group consisting of ammonia and nitrogen.
6. The method of claim 1 , wherein the plurality of metal catalyst nanoclusters are made of a metal selected from the group consisting of Ni, Au, Pt, Ga, In, Co, and Fe.
7. The method of claim 1 , wherein the step of forming the plurality of metal catalyst nanoclusters comprises:
depositing up to approximately a monolayer of catalyst metal atoms on the surface of the crystallographic template substrate; and
heating the crystallographic template substrate in a reducing atmosphere to induce surface diffusion of the catalyst metal atoms to form the plurality of metal nanoclusters.
8. The method of claim 1 , wherein the step of forming the plurality of metal catalyst nanoclusters comprises:
depositing catalyst metal atoms on the surface of the crystallographic template substrate; and
heating the crystallographic template substrate in a reducing atmosphere to induce surface diffusion of the catalyst metal atoms to form the plurality of metal nanoclusters.
9. The method of claim 1 , wherein the step of forming the plurality of metal catalyst nanoclusters comprises:
depositing a solution comprising a solvent and a salt of metal catalyst ions onto the surface of the crystallographic template substrate;
removing the solvent; and
heating the crystallographic template substrate in a reducing atmosphere to reduce the metal catalyst ions to catalyst metal atoms and to induce surface diffusion of the catalyst metal atoms to form the plurality of metal nanoclusters.
10. The method of claim 1 , wherein the nanowire growth conditions comprise a substrate temperature between approximately 650° C. and approximately 950° C. and wherein the lateral growth conditions comprise a substrate temperature between approximately 900° C. and approximately 1150° C.
11. The method of claim 1 , wherein the coalesced Group III nitride layer comprises at least one Group III species selected from the group consisting of Al, Ga, and In.