A semiconductor structure includes a first layer of a nitride semiconductor material, a substantially unstrained nitride interlayer on the first layer of nitride semiconductor material, and a second layer of a nitride semiconductor material on the nitride interlayer. The nitride interlayer has a first lattice constant and may include aluminum and gallium and may be conductively doped with an n-type dopant. The first layer and the second layer together have a thickness of at least about 0.5 μm. The nitride semiconductor material may have a second lattice constant, such that the first layer may be more tensile strained on one side of the nitride interlayer than the second layer may be on the other side of the nitride interlayer.