Internal mechanical strain and defects in Si crystals implanted with Ge⁺ ions over the dose range 10¹⁰-3 × 10¹⁵ cm^-2 have been studied. The strain after the annealing cycles was investigated by high-resolution x-ray diffraction; the defects with deep levels in the bandgap were investigated by deep level transient spectroscopy. In the as-implanted samples and at low annealing temperatures vacancy-related defect complexes with deep levels in the gap are associated with the mechanical strain induced by isolated amorphous inclusions. In the temperature range 500-900 °C the dominant defects are Ge-containing complexes. At high annealing temperatures (700-900 °C) deep level traps associated with the boundaries between the recrystallized regions and the rest of the crystal are formed and a corresponding strain profile is created.