LATTICE DAMAGE IN ION-IMPLANTED SILICON-GERMANIUM ALLOYS

The damage produced in Si1-xGex alloys (0 less-than-or-equal-to x less -than-or-equal-to 1) by implantation of 70-100 keV Si-30+ has been mea sured as a function of temperature and fluence by ion channeling. For all compositions, the damage efficiency decreased sharply as the impla nt temperature was increased between room temperature and 150-degrees- C. Furthermore. the damage efficiency in alloys of intermediate compos itions (0.35 less-than-or-equal-to x less-than-or-equal-to 0.5) exceed s that in Ge, especially at elevated temperatures, despite the larger cascade energy density in Ge. It is shown that this behavior can be de scribed based on a model in which the point defect mobility is the dom inant factor controlling damage retention, rather than the cascade ene rgy density. This approach provides a framework for understanding othe r temperature-dependent phenomena related to damage growth in Si-Ge al loys including dose rate effects and damage saturation in MeV implanta tion.