Origination of misfit dislocations at the surface during the growth of GeSi/Si(001) films by low-temperature (300–400°C) molecular-beam epitaxy

The method of the molecular-beam epitaxy, at comparatively low temperatures (300–400°C), was used to grow Ge_xSi_{1 ? x} /Si(001) films with a constant composition (x = 0.19–0.32) across a film and as well as two-layer heterostructures with the Ge content at the upper layer no lower than 0.41. Using transmission electron microscopy, it is shown that the main cause of an increase in the density of threading dislocations with increasing Ge fraction in the plastically relaxed films is the origination of the dislocation half-loops at the film surface; in turn, these dislocation half-loops are generated owing to the formation of a three-dimensional profile at the surface of the growing or annealed film.