Patent ID: 8729559

Claim:
A method for forming a biaxially relaxed c-plane epitaxial Al x In y Ga (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 Al x In y Ga (1-x-y) N epitaxial layer on the isolated regions, comprising: growing a strained epitaxial Al x In y Ga (1-x-y) N region on the isolated regions, wherein at least during initial stages of growth the strained epitaxial Al x In y Ga (1-x-y) N region comprises a plurality of misfit dislocations; and increasing a thickness of the at least one epitaxial Al x In y Ga (1-x-y) N layer to cause the isolated regions to close off by lateral growth and to form a coalesced epitaxial Al x In y Ga (1-x-y) N region, wherein the coalesced epitaxial Al x In y Ga (1-x-y) N region is substantially free of misfit dislocations; and forming at least one biaxially relaxed c-plane epitaxial Al x In y Ga (1-x-y) N layer overlying the coalesced epitaxial Al x In y Ga (1-x-y) N region, wherein a total thickness of the at least one epitaxial Al x In y Ga (1-x-y) N layer is at least 100 nm; and the biaxially relaxed c-plane epitaxial Al x In y Ga (1-x-y) N layer is characterized by a biaxial strain less than 0.1% and a total threading dislocation density less than 10 8 cm −2 .