Rearrangement of misfit dislocations in GaAs on Si by post-growth annealing

Abstract

The effects of post-growth annealing have been investigated on the movement and rearrangement of two different groups of misfit dislocations in molecular beam epitaxially grown GaAs on tilted (3° toward [110]) Si(001) substrates by using transmission electron microscope. The group I misfit dislocations show a cross-grid structure running along two 〈110〉 directions at the interface and are already formed in small islands of 20–30 nm in size. The spacing of ∼ 9.5 nm between the dislocations along each 〈110〉 is constant throughout all of the growth stages from 10 nm to 3 μm in GaAs thickness, although the cross grid pattern becomes more clear and regular due to annealing treatment. On the other hand, the group II misfit dislocations show short and segmented structures approximately along the 〈110〉 directions, which we consider to be related to threading dislocations. They are very mobile, and gradually become rearranged with the extension of their length along the 〈110〉 directions near to the interface, as the annealing temperature increases. The group I and II misfit dislocations are thought to be generated due to stresses caused by the lattice misfit and the thermal expansion misfit between GaAs and Si, respectively.