Zero-strain GaAs quantum dot molecules as investigated by x-ray diffuse scattering

The authors report on x-ray diffuse scattering at nominally strain-free GaAs(001) quantum dot molecules (QDMs). Al0.3Ga0.7As deposited by molecular beam epitaxy on GaAs(001) acts as barrier layer between the GaAs(001) substrate and subsequently grown QDMs; the adjusted thickness of 50 nm preserves the in-plane lattice parameter. Pairs of lenselike quantum dots are created with preferential orientation along [1 (1) over bar0] placed on shallow hills. Grazing incidence diffraction along with kinematical scattering simulations indicate completely strain-free QDs which prove a strongly suppressed intermixing between QDMs and the underlying AlGaAs barrier layer.