DISLOCATION INTERACTIONS IN CDTE/GAAS GROWN BY HOT WALL EPITAXY WITH CDTE/CDZNTE SUPERLATTICES

CdTe epilayers grown on GaAs (001) containing two CdTe/CdZnTe superlattices (SLSs) have been examined by TEM. The overall dislocation-reduction effect from plan-view measurements is found to be 2.5 times, with the bending of threading dislocations occurring largely at the top and bottom layers in each of the SLSs. However, it is found that a large number of threading dislocations in the epilayer exist in the form of dipole pairs. In particular, long straight dislocations (LSDs) originating from the interface region are almost always close dipole pairs with typical spacings of less than 10 nm between the components. A model is presented to explain the formation of such LSD dipoles at the early stages of growth. It is proposed that dislocations with opposite Burgers vectors gliding on parallel {111} planes interact to form close dipole pairs elongated in <112> directions. It is shown that the pairing of dislocations in this manner reduces the effectiveness of SLS layers in dislocation filtering. In addition, the dislocations in the dipole pairs are frequently found to be dissociated into two partial dislocations. These effects complicate the dynamics of dislocations in CdTe/GaAs and may place a serious constraint on the ability of SLSs to remove threading dislocations from these epilayers.