DYNAMICAL FORMATION PROCESS OF PURE EDGE MISFIT DISLOCATIONS AT GAAS SI INTERFACES IN POSTANNEALING/

We investigate the dynamical formation process of pure edge misfit dis locations (90 degrees type) in GaAs/Si(100) (3 degrees off toward [011 ]). The cross sections at the interfaces of GaAs/Si annealed at variou s temperatures (300-600 degrees C) are observed by high-resolution tra nsmission electron microscopy. The pure edge dislocation is formed by the reaction of two mixed dislocations (60 degrees type) at the interf ace, and is not introduced directly from the epilayer surface. To expl ain the experimental results, we present a new formation process of pu re edge dislocations: (1) glide from the epilayer surface, (2) climb a long the interface and (3) reaction. In this process, the climb motion along the interface is most important. In addition, the difference in the ratio of pure edge dislocations to the total dislocations was obs erved between stepped and flat directions of the Si substrate. This as ymmetry may be caused by the difference in climb velocities along the interface. The Si surface steps probably enhance this climb motion.