Effectiveness of strained-layer superlattices in reducing defects in GaAs epilayers grown on silicon substrates

In GaAs-GaAsP strained-layer superlattices grown lattice matched to GaAs are effective buffer layers in reducing dislocations in epitaxial GaAs films grown on Si substrates. The strained-layer superlattice structure permits high values of strain to be employed without the strained-layer superlattice generating dislocations of its own. We find that the strained-layer superlattice buffer is extremely effective in blocking threading dislocations of low density and is less effective when the dislocation is high. It appears that for a given strained-layer superlattice there is a finite capacity for blocking dislocations. Transmission electron microscopy has been used to investigate the role of the superlattice buffer layer.