Experimental observation of motion of edge dislocations in Ge/GexSi1–x/Si(001) (x = 0.2–0.6) heterostructures

Abstract

The Ge/Ge_xSi_1–x/Si(001) (x = 0.2–0.6) heterostructures grown by the molecular epitaxy method are analyzed using high-resolution electron microscopy with atomic resolution. The thickness of the Ge_xSi_1–x buffer layer is 7–35 nm. It is shown that such heterostructures relax in two stages: an ordered network of edge dislocations is formed during their growth (500°C) at the Ge/GeSi interface and then, contrary to the generally accepted opinion concerning their immobility, some of the edge dislocations move through the buffer GeSi layer to the GeSi/Si(001) interface during annealing at higher temperatures and x > 0.3. It is found that plastic relaxation of the GeSi buffer layer occurs due to motion of dislocation complexes of the edge type, consisting of a pair of complementary 60° dislocations with the ends of {111} extra planes located approximately at a distance from 2 to 12 interplanar spacings. It is shown that the penetration of dislocation complexes into the GeSi buffer layer and further to the GeSi/Si interface is intensified with increasing annealing temperature (600–800°C) and the fraction of Ge in the buffer layer.