Relationship between V/III ratio and generation of defects in MOVPE grown (001) GaAs/Ge heterostructures

TEM is used to study the generation of defects in MOVPE grown GaAs/Ge heterostructures as a function of the V/III ratio. Misfit dislocations are present in the layers grown with low V/III. Their dissociation often produces stacking faults whose density increases with decreasing V/III. This result is explained by the effect of the unintentional Ge doping from the substrate on the motion of the partials bordering the stacking faults. Misfit dislocations are not detected in the layers grown with high V/III (high growth rate), up to a layer thickness of 1.3 mu m. These layers, however, contain a high density of planar defects very likely because island growth has occurred.