Distribution and shape of self-assembled InAs quantum dots grown on GaAs (001)

Grazing incidence small angle X-ray scattering (GISAXS) and atomic force mi croscopy (AFM) experiments are employed to study self-assembled InAs quantu m dots (QDs) grown by molecular beam epitaxy (MBE) on GaAs (001). The GISAX S spectra show pronounced non-specular diffuse scattering satellite peaks w ith high diffraction orders up to +/-3 along [110], [1-10], and [100] sampl e azimuthal orientations with respect to the incoming beam, indicating a la teral ordering of the InAs QDs. The con-elation lengths of the lateral dot distribution are found to be identical along [110] and [1-10] but smaller a long [100] direction. The ratio of the mean dot-dot distances along [100] a nd [1-10] azimuths is determined to be 1.13, indicating the anisotropic ord ering of QD distribution. Broad diffraction peaks are observed at larger sc attering angles and associated to dot facet crystal truncation rods (CTR). We determine {111}-like facets along [110] and [1-10] sample azimuths, and {101}-like facets along [100] azimuth.