The ability of radiation enhanced quantum well (QW) intermixing to produce active integrated photonic devices has been demonstrated by the manufacture of a set of wavelength tuned lasers from a single semiconductor wafer. Defects, created in the InP-based structure by a high energy (1 MeV) P implant, enhance the diffusion of atomic species across the as-grown heterojunctions during subsequent rapid thermal annealing (90 s at 700°C). As a result, the QW band gap energy is blue shifted with respect to unirradiated regions. It is shown that by implanting through a SiO 2 mask of varying thickness, the bandgap of the QW can be selectively tailored across the wafer. Additional results from GaAs- and SiGe-based QW systems are presented to illustrate how bandgap engineering techniques may be improved through a better understanding of the defect interactions involved. In the GaAs-based structure, defect trapping at structural interfaces has been identified as a possible hindrance to ion assisted intermixing. In contrast, data from the group IV QWs highlights the benefits of a low temperature (24 h at 630°C) anneal prior to irradiation. By removing defects from the as-grown material with pre-annealing, the relative bandgap shift induced by ion bombardment is doubled.