THE COHERENCY LOSS MICROSTRUCTURE AT A CDTE/GAAS(001) INTERFACE

The dislocation microstructure associated with the loss of coherency of CdTe(001), as grown on GaAs(001), is characterized using high-resolution transmission electron microscopy. The examination of cross-sectional specimens allowed characteristic local variations in the relative orientation of the overgrowth and the substrate to be quantified and related to associated local changes in the form and distribution of the interface dislocation array. In the interface array, the relative proportion of 60-degrees dislocations and Lomer-Cottrell locks proved to be related to the local misorientation between the CdTe and GaAs. The extent to which this is indicative of the mode of stress relief during the loss of coherency is discussed. Interestingly, it was also found that such variations in the relative proportions of the different types of dislocation proved to be associated with microtwin formation. The significance of this with regard to the strain relief mechanism is also noted.