A semiconductor layer structure may include a substrate, a buffer layer formed on the substrate, and a set of epitaxial layers formed on the buffer layer. The buffer layer may have a thickness that is greater than 2 micrometers (μm). The set of epitaxial layers may include a quantum well layer. A quantum well intermixing region may be formed in association with the quantum well layer and a material diffused from a region of a surface of the semiconductor layer structure.