Method for quantum well intermixing using pre-annealing enhanced defects diffusion

A method of making a multiple bandgap semiconductor device, comprising the steps of:

• forming a quantum well structure, wherein the quantum well structure comprises a plurality of epitaxial layers disposed over a substrate including a quantum well layer disposed between upper and lower barrier layers;
• forming a patterned mask over the quantum well structure with sufficient thickness to block ions incident thereon, wherein the patterned mask includes a plurality window portions of reduced thickness for passing therethrough at least some ions incident thereon;
• heating the quantum well structure to a first elevated temperature;
• bombarding the patterned mask with ions, wherein at least some of the ions incident on the window portions pass therethrough and are introduced into the heated quantum well structure;
• thermally pre-annealing the quantum well structure at a second elevated temperature and for a pre-annealing time period that do not induce quantum well intermixing in the quantum well structure;
• and
• thermally annealing the quantum well structure at a third elevated temperature greater than the second elevated temperature, and for an anneal time period, sufficient to induce quantum well intermixing in, and a shifting of a bandgap energy of, the quantum well layer.