Low-temperature strain relaxation in ion-irradiated pseudomorphic SiGe/Si structures

The effect of non-equilibrium point defects on strain relaxation in pseudomorphic Si0.76Ge0.24/Si heterostructures was studied by X-ray diffraction (XRD) and low-temperature photoluminescence (PL). The overcritical Si0.76Ge0.24 layer was grown by molecular beam epitaxy at relatively low temperature in order to avoid strain relaxation during the growth and then the non-equilibrium point defect were introduced by Ge+ ion implantation. The samples were annealed in the temperature range from 500 to 600 °C. The ion-irradiated heterostructures showed considerably different relaxation behavior than the unimplanted samples. For the same heat-treatment conditions, the degree of relaxation was found to increase as the implantation dose rose.