Strain relaxation of Ge-implanted silicon wafers

In this work, Ge has been introduced into silicon wafers by ion implantation method to acquire surface-layer tensile strain. It has been demonstrated that there are different strain states among Ge-implanted silicon wafers with different implantation conditions: (1) high dose of 7 × 1016 cm−2 at room temperature; (2) high dose of 7 × 1016 cm−2 at liquid nitrogen temperature; (3) low dose of 6 × 1014 cm−2 at room temperature. It is demonstrated that the Ge-graded profile and such structures as the half-loop dislocations and Ge-rich nanoclusters may correlate with the appearance of few defects and the preservation of the elastic tensile strain in the surface layer of the first set of samples. In the second and third sets of samples no noticeable strains do appear. The reason of this behaviour might be ascribed to a large number of defects penetrating outside the surface and the low fraction of Ge, respectively.