Competing mechanisms of strain relaxation in Ge/Si(001) heteroepitaxy

Atomistic simulation with semiempirical Stillinger-Weber potential has been used to study the energetics of strain relaxation in Ge/Si(001) heteroepitaxial system. Several alternative scenarios for misfit strain relief through dislocation nucleation have been investigated. Minimal energy path for each transition trajectory has been found using combination of modified DRAG and Nudged Elastic Band methods. Our results showed that standard 90° Lomer dislocation is the most favorable (global minimum) defect for this heteroepitaxial system. Alternative more complex defects containing two shifted 60° dislocations are indeed also local minima for this system, however corresponding to higher energy states. Their appearance in experiments might be the result of growth kinetics.