Dislocation structure formation in SiGe/Si(001) heterostructures with low-temperature buffer layers

Abstract

Mechanisms of misfit dislocation generation as well as peculiarities of dislocation structure formation in Si0.7Ge0.3/Si multilayer heterostructures grown by molecular beam epitaxy with low-temperature (LT) SiGe and (SiGe + Si) buffer layers were studied. Full strain relaxation in the heterostructures with 200–250 nm thick buffer layers has been achieved. In the heterostructures with both types of LT layer, misfit dislocation generation is found to proceed similarly to heterostructure growth at high temperatures; however, the rate of dislocation nucleation is higher due to the high vacancy concentration near the interface. Threading dislocations, which are not connected with misfit dislocation network, are generated in the epitaxial layers apart from the SiGe–Si interface to form a dislocation density of 107–108 cm−2 on the surface.