Implantation induced changes in quantum well structures

Ion-beam induced intermixing of quantum wells and superlattices is of use in the fabrication of low dimensional structures by spatially restricted ion implantation. The ultimate size of quantum lines or dots is determined by the spatial extent of the intermixing due to individual ion impacts and subsequent annealing. We show by photoluminescence measurements that complete intermixing of implanted and annealed GaAs/GaAlAs interfaces takes place at a very low dose (≈ 10¹¹ cm^-2). This enables us to deduce intermixing radii, following annealing, of 20-30 nm for the affected area due to individual ion impacts. These radii are about one order of magnitude larger than the damage track prior to annealing. The exceptionally large radii found in the present work are attributed to defect assisted interdiffusion. The low doses for mixing also support the particle channeling explanation for ion induced mixing at depths in excess of the amorphous range.