Method of making bulk InGaN substrates and devices thereon

A method for forming a biaxially relaxed c-plane epitaxial AlxInyGa(1-x-y)N layer comprising:

• providing a substrate having a surface characterized by an orientation within 5 degrees of a c-plane;
• forming a pattern of channels in the substrate and isolated regions of the substrate defined by the channels, wherein
• the channels are characterized by a sidewall angle with respect to the surface of the isolated regions between 60 degrees and 90 degrees and a pitch ranging from between 10 nm and 1000 nm;
• and
• a surface of the isolated regions is characterized by an orientation within 5 degrees of a c-plane;
• growing at least one AlxInyGa(1-x-y)N epitaxial layer on the isolated regions, comprising:
• growing a strained epitaxial AlxInyGa(1-x-y)N region on the isolated regions, wherein at least during initial stages of growth the strained epitaxial AlxInyGa(1-x-y)N region comprises a plurality of misfit dislocations;
• and
• increasing a thickness of the at least one epitaxial AlxInyGa(1-x-y)N layer to cause the isolated regions to close off by lateral growth and to form a coalesced epitaxial AlxInyGa(1-x-y)N region, wherein the coalesced epitaxial AlxInyGa(1-x-y)N region is substantially free of misfit dislocations;
• and
• forming at least one biaxially relaxed c-plane epitaxial AlxInyGa(1-x-y)N layer overlying the coalesced epitaxial AlxInyGa(1-x-y)N region, wherein
• a total thickness of the at least one epitaxial AlxInyGa(1-x-y)N layer is at least 100 nm;
• and
• the biaxially relaxed c-plane epitaxial AlxInyGa(1-x-y)N layer is characterized by a biaxial strain less than 0.1% and a total threading dislocation density less than 108 cm−2.