Gallium-implantation-enhanced intermixing of close-surface GaAs/AlAs/AlGaAs double-barrier quantum wells

The intermixing of close-surface GaAs/AlAs/AlGaAs double-barrier quantum wells by a 50 keV Ga+ implantation has been studied both experimentally and theoretically. It was found that for already low Ga+ implantation doses (≤1012 cm−2) a considerably broadened emission peak with an appreciable luminescence blue shift can be obtained. For medium implantation doses (≊1013 cm−2) very large blue shifts in the range of 200 meV were observed, which still retain a reasonable emission intensity. For high Ga+ implantation doses (≥3×1014 cm−2) total intermixing occurs and no photoluminescence can be recovered due to efficient Γ–X scattering. The photoluminescence blue shifts of lower-dose implantations are not influenced by the annealing temperature, whereas the blue shift of higher-dose implantations depend very much on the annealing conditions. The measured data support a heterogeneously enhanced interdiffusion based on a defect cluster model. The importance of a tight control of the annealing ambient and the sample surface condition is discussed.