Defects in epitaxial multilayers I. Misfit dislocations

Multilayers composed of many thin films of GaAs and GaAs 0·5 P 0·5 were grown epitaxially on GaAs surfaces inclined at a few degrees to (001). Examination of the multilayers by transmission and scanning electron microscopy has revealed that the interfaces between layers were made up of large coherent areas separated by long straight misfit dislocations. The Burgers vectors of the dislocations were inclined at 45° to (001) and were of type 1/2a . Dislocations in adjacent interfaces were usually not independent of one another. They often lay on the same slip plane and when this was so they were clearly products of the same source. The layer thickness at which misfit dislocations were formed was in satisfactory agreement with the predicted thickness. However, the fraction of the total misfit accommodated by dislocations (once the critical thickness for dislocation generation was passed) was much smaller than predicted. This large discrepancy seems to arise from difficulties associated with the creation of misfit dislocations. Although there are many processes which can impede dislocation generation, the most important one in GaAs/GaAs 0·5 P 0·5 multilayers appears to be the impaction of dislocations on one glide plane against dislocations in another.