Threading dislocations in GaAs grown with free sidewalls on Si mesas

We have studied the mechanisms that determine the density and structure of threading dislocations (TDs) in GaAs on Si by growing GaAs films on continuous Si substrates and on 10–34‐μm‐wide Si mesas that provided free‐sidewall growth. The effects of a soft ZnSe interlayer and of postgrowth annealing to 850 °C were also investigated. TD densities were accurately determined using large area plan‐view transmission electron microscopy. Burgers vector analysis of the TDs showed that threading segments associated with both sessile 90° misfit dislocations and glissile 60° misfit dislocations were present after growth. A difference in dislocation structure between the annealed and unannealed samples was observed. It was also found that the dislocations were unaffected by proximity to free sidewalls and by the ZnSe interlayer. The results indicate that dislocation interactions during the early stages of growth determine the structure and density of TDs in as‐grown films. It was also concluded that plastic relaxatio...