Characterization of extended defects in SiGe alloys formed by high dose Ge implantation into Si

The synthesis of SiGe/Si heterostructures by Ge⁺ ion implantation is reported. 400 keV Ge⁺ ions were implanted at doses ranging from 3 × 10¹⁶ to 10 × 10¹⁶ ions/cm² into (001) Si wafers, followed by Si⁺ amorphisation and low temperature Solid Phase Epitaxial Regrowth (SPER). TEM investigations show that strained alloys can be fabricated if the elastic strain energy (E_el) of the SiGe layer does not exceed a critical value (E′_el) of about 300 mJ/m², which is independent of the implantation energy. Our analysis also suggests that “hairpin” dislocations are formed as strain relieving defects in relaxed structures. A “strain relaxation” model is proposed to explain their formation.