Observation of partial relaxation mechanisms via anisotropic strain relief on epitaxial islands using semiconductor nanomembranes

In this work we attempt to directly observe anisotropic partial relaxation of epitaxial InAs islands using transmission electron microscopy a and synchrotron x-ray diffraction on a 10 nm thick InAs:GaAs nanomembrane.... [ view full abstract ]

In this work we attempt to directly observe anisotropic partial relaxation of epitaxial InAs islands using transmission electron microscopy a and synchrotron x-ray diffraction on a 10 nm thick InAs:GaAs nanomembrane. Figure 1 and 2 show TEM and x-ray diffracion measurements of the herostructure explored in this paper. We show that under such conditions TEM provides improved real-space statistics, allowing the observation of partial relaxation processes that were not previously detected by other techniques or by usual TEM cross section images. These results can be seen in Figure 3. Besides the fully coherent and fully relaxed islands that are known to exist above previously established critical thickness, we prove the existence of partially relaxed islands, where incomplete 60° half-loop misfit dislocations lead to a lattice relaxation along one of the 〈110〉 directions, keeping a strained lattice in the perpendicular direction. These growning processes are sketched in Figure 4. Although individual defects cannot be directly observed, their implications to the resulting island registry are identified and discussed within the frame of half-loops propagations.