Extended defects in GaAs/GaAs_1-xSb_x/GaAs (001) heterostructures

The atomic-scale structure of extended defects in GaAs/GaAs_1-xSb_x/GaAs (001) heterostructures has been characterized using aberration-corrected scanning transmission electron microscopy. The defect located at the tensile-strained GaAs(cap)/GaAs_0.34Sb_0.66 interface had no edge component in the {11¯0} projection plane and is identified as either a dissociated screw dislocation or a partial dislocation dipole. The associated intrinsic stacking fault is bounded by two 30° Shockley partial dislocations of opposite sign. Another defect, located at the compressively-strained GaAs_0.91Sb_0.09/GaAs(substrate) interface, is identified as a dissociated 90° dislocation. The associated intrinsic stacking fault is bounded by a 30° Shockley partial dislocation and a partial dislocation with a Burgers vector of either a/6[411¯] or a/6[141¯], where a is the lattice constant. Unpaired atomic columns observed at the cores of the 30° Shockley partial dislocations indicate that both defects belong primarily to the glide set.