An optical semiconductor device such as a light emitting diode is formed on a transparent substrate having formed thereon a template layer, such as AlN, which is transparent to the wavelength of emission of the optical device. A mixed alloy defect redirection region is provided over the template layer such that the composition of the defect redirection region approaches or matches the composition of the regions contiguous thereto. For example, the Al content of the defect redirection region may be tailored to provide a stepped or gradual Aluminum content from template to active layer. Strain-induced cracking and defect density are reduced or eliminated.