The influence of ion mass and dose on the intermixing of GaAs/GaAlAs quantum‐well structures using photoluminescence (PL) and secondary‐ion‐mass spectroscopy (SIMS) techniques has been studied. Ga, Zn, Ar, Mg, Ne, and He ions are implanted in a single‐quantum‐well (SQW) structure at different doses. After annealing, the amount of intermixing between Al and Ga is extracted from the PL peak energy shift of the near‐band‐gap emission of the SQW. The measured Al diffusion length values &Dgr;Alfor different ion species agree with a simple model which assumes that the implantation damage in conjunction with lowT(T<600 °C) defect diffusion is responsible for the mixing. We observe a similar dose dependence for &Dgr;Alfor all the above ions. For high implantation doses we have studied the mixing by Ar ions after implantation and annealing with SIMS. The SIMS data indicate that at high doses collisional mixing is the dominant mechanism for the disordering. Drastic mixing effects are obtained in the above quantum‐well structures after high‐temperature annealing of samples implanted with electrically active impurities (S,Si).