THREADING DISLOCATIONS IN GAAS ON SI GROWN WITH SIMILAR-TO-1 NM THICKSI INTERLAYERS

Threading dislocation morphologies and characteristics have been inves tigated in 3 mu m thick GaAs films with ultrathin(similar to 1 nm) Si interlayers grown by molecular beam epitaxy on tilted (2 degrees towar d [110]Si (001) substrates using cross-sectional transmission electron microscopy. Four sample structures are studied in which different num bers of ultrathin Si layers are grown at different positions in the Ga As film, and the results are compared for samples observed before and after ex situ annealing. In all of the sample structures, some mixed-t ype dislocations are clearly blocked by the Si interlayers, although s ome of them pass through these layers, resulting in propagation of the ir threading dislocations to the sample surface. After annealing at 90 0 degrees C for 10 s or 800 degrees C for 30 min, the interactions of the dislocations with the interlayers are enhanced, and there is an in crease in the number of dislocations which are bent along the [110] di rections at the positions of the Si barrier layers. However, a conside rable number of dislocations still escape from the Si barriers by glid ing on {111} slip planes during annealing. Moreover, ex situ annealing generates new edge-type dislocations through interactions between mov ing threading dislocations. The nature of the dislocations that cross the Si barriers is especially discussed.