Strain relaxation of pseudomorphic Si_1-xGe_x/Si(100) heterostructures after Si⁺ ion implantation

The strain relaxation of pseudomorphic Si_1-xGe_x layers (x=0.21,…,0.33) was investigated after low-dose Si⁺ ion implantation and annealing. The layers were grown by molecular-beam epitaxy or chemical vapor deposition on Si(100) or silicon-on-insulator. Strain relaxation of up to 75% of the initial strain was observed at temperatures as low as 850 °C after implantation of Si ions with doses below 2×10¹⁴ cm^-2. We suggest that the Si implantation generates primarily dislocation loops in the SiGe layer and in the underlying Si which convert to strain relaxing misfit segments. The obtained results are comparable to strain relaxation achieved after He⁺ implantation with doses of 1–2×10¹⁶ cm^-2.