RADIATION-DAMAGE OF 2 MEV SI IONS IN SI0.75GE0.25 OPTICAL MEASUREMENTS AND DAMAGE MODELING

The radiation damage of MBE grown relaxed Si0.75Ge0.25 layers after im plantation with 2 MeV Si+ ions at room temperature has been measured f or the first time using optical reflectivity depth profiling on small angle bevelled samples. Disregarding a significantly larger damage eff iciency, the dose dependence of damage at the maximum of damage profil es is similar to that observed for equivalent Si+ self-implantations a nd can be mathematically described by means of a model proposed by Hec king et al. [Nucl. Instr. and Meth. B15 (1986) 760] for these self-imp lantations. From a comparison of model parameters it is concluded that the higher damage efficiency in the alloy is mainly based on a strong er formation of amorphous volume fractions rather than on a stronger p roduction of point defect type damage. In addition, model calculations indicate an enhanced point defect recombination as compared to pure S i.