Patent ID: 7825432

Claim:
A semiconductor structure, comprising: a nucleation layer comprising aluminum nitride; a graded layer on the nucleation layer, wherein the graded layer is graded from a composition including Al x Ga 1-x N adjacent the nucleation layer, wherein x decreases with distance from the nucleation layer; a first layer of a nitride semiconductor material on the graded layer; a substantially relaxed nitride interlayer on the first layer of nitride semiconductor material, the substantially relaxed nitride interlayer having a first lattice constant, wherein the nitride interlayer comprises aluminum and gallium and is conductively doped with an n-type dopant; and a second layer of the nitride semiconductor material on the nitride interlayer; wherein the nitride interlayer comprises a plurality of discrete portions therein, wherein the discrete portions have a material composition that is different than a material composition of the nitride interlayer and wherein the nitride interlayer has a first bandgap and the discrete portions have a second bandgap that is lower than the first bandgap.