TRANSMISSION ELECTRON-MICROSCOPY INVESTIGATION OF DISLOCATION BENDING BY GAASP/GAAS STRAINED-LAYER SUPERLATTICES ON HETEROEPITAXIAL GAAS/SI

A systematic study, investigating the effects of strained-layer superlattices (SLSs) on threading dislocations present in GaAs/Si heteroepitaxial layers, was conducted. Transmission electron microscope contrast analysis was performed on ∼1% lattice-mismatched GaAs0.72P 0.28/GaAs SLSs grown on GaAs/Si substrates.Threading dislocations were found to have Burgers vectors inclined to the GaAs/Si interface. Individual strained layers ranging in thickness from 100 to 250 Å were observed to have negligible effect on dislocation bending. Instead, dislocation bending occurred primarily at the first and last interfaces of the SLS packets. Similarly, effective dislocation bending was observed using 1000 Å layers. Threading dislocation density close to the GaAs/Si heterointerface was found to depend on the SLS packet proximity to the interface.