Interpretation of the depth-dependent etch-pit density in InGaAs/GaAs heterostructures

We study the defect structure of MBE-grown (100) InGaAs/GaAsmismatched heteroepitaxial layers by selective electrochemical
(anodic) etching. By incremental layer removal, we map the
depth profile of the etch pit density. The defect density is
inversely proportional to the layer thickness and increases
with In content. The results are explained by a quantitative
theoretical model of threading dislocation annihilation. The
importance of the layer residual strain in the annihilation
process is shown.