Lattice damage of relaxed Si1-xGex alloys of various composition implanted with 2 MeV Si ions

The accumulation of damage in relaxed Si1-xGex alloys (0.04 less than or equal to x less than or equal to 0.36) after 2 MeV Si ion implantation at 300 K has been studied by optical reflectivity depth profiling (ORDP). Damage is observed to increase with increasing Ge content of the alloy. While for sufficiently low doses the shape of damage profiles is similar to that of the nuclear stopping power for all Ge concentrations, composition dependent changes in profile shape are observed at doses where defects produced in different collision cascades may interact. For the depth of maximum damage the dose dependence of damage is described by a model. From the model parameters it is concluded that the stronger damage in the Ge rich alloys is mainly due to a stronger production of amorphous portions in individual collision cascades.