Behavior of Dopant-Related Defects in AlGaAs Superlattices

During the course of investigation of the mixing of highly silicon-doped GaAs/AlAs superlattices, defects such as dislocation loops and Si-rich precipitates were found to form in the specimens. These defects formed at particular doping levels upon annealing of the samples. The presence of the defects can be related to changes in mixing behavior. In the present study, transmission electron microscopy has been used to characterize the defects. Superlattices with varying silicon doping levels were annealed at different temperatures for varying time-periods, to observe the temperature-time behavior of the dislocation loops. The defects aggregate preferentially in the GaAs as opposed to the AlAs in the superlattice. A number of the dislocation-loops were investigated using high-resolution TEM. All the loops observed were interstitial in nature.