EFFECTS OF LOW-TEMPERATURE PREANNEALING ON ION-IMPLANT ASSISTED INTERMIXING OF SI1-XGEX SI QUANTUM-WELLS/

Using photoluminescence we have studied the effect of a low temperatur e ''preanneal'' stage on the intermixing of 3 nm Si0.7Ge0.3/Si quantum wells, implanted with silicon ions having energies up to 1 MeV and th en exposed to rapid thermal annealing at 850 degrees C for 300 s. We f ind that an unwanted quantum well band gap increase in unimplanted sam ples after rapid thermal annealing can be reduced substantially from s imilar to 30 to similar to 5 meV due to the removal of grown-in defect s by preannealing at 630 degrees C for 24 h. Preannealed samples that were implanted and rapid thermal annealed showed at least the same ban d gap increase (up to 70 meV in these samples) observed for nonpreanne aled samples. These results are understood in terms of significantly d ifferent activation energies for defect diffusion and quantum well int ermixing and a nonlinear dependence of the energy shifts on defect con centrations. (C) 1996 American Institute of Physics.