Relaxed SiGe heteroepitaxy on Si with very thin buffer layers: experimental LEPECVD indications and an interpretation based on strain- dependent dislocation nature

Low-energy plasma-enhanced chemical vapor deposition experiments indicate that strain relaxation in thin virtual SiGe layers grown abruptly on a Si substrate may occur more efficiently than in thick graded layers. We provide one possible explanation using molecular dynamics simulations based on Tersoff potentials, showing that the mobility of shuffle dislocation segments is enhanced with increasing misfit in Ge/SiGe(001) alloys. A low strain regime favors the formation of partialized glide segments. The simulated mobility of the perfect shuffle core, in the case of strong compressive stress, appears to be extremely high. Despite being qualitative in nature, these results suggest an intriguing interpretation of the experimental observation.