A process for shifting the bandgap energy of a quantum well layer (e.g., a III-V semiconductor quantum well layer) without inducing complex crystal defects or generating significant free carriers. The process includes introducing ions into a quantum well structure at an elevated temperature, for example, in the range of from about 200 C. to about 700 C. The quantum well structure that has had ions introduced therein includes upper and lower barrier layers with quantum well layers therebetween. The quantum well structure is then pre-annealed at a temperature and time that does not induce quantum well intermixing, but does diffuse the point defects closer to the quantum well layer. Finally, the structure is thermally annealed at a higher temperature to induce quantum well intermixing (QWI) in the quantum well structure, which shifts the bandgap energy of the quantum well layer.