Anisotropic distribution of crystalline defects along [011] and [011] directions in In 0.52 AI 0.48 As buffer layers grown on InP

Layers of In_0.48Al_0.52As grown by molecular beam epitaxy (MBE) on InP (100) substrates have been examined by transmission electron microscopy (TEM). At a low growth temperature (Tg=300°C) a {111} microtwinned structure was observed, the origin of which has been explained taking into account the limited kinetics of group III atoms and the differences in the propagation speed of the surface steps during MBE growth. For growth temperatures in the range 440–530°C, the defect densities decrease monotonically; threading dislocations and stacking faults on the {111} and {111} planes are the prevailing types of defect. The asymmetry of fault densities between the {111} and {111} planes has been discussed on the basis of the different mobilities of the partial dislocations bordering the faults.