Determination of 2D pair correlations and pair interaction energies of In atoms in molecular beam epitaxially grown InGaAs alloys

Intra- and interlayer atom-atom correlations in molecular beam epitaxially grown dilute InGaAs alloys were studied using cross-sectional scanning tunneling microscopy. By imaging individual chemical constituents we construct a large ensemble of ''atom maps'' from which two-dimensional In-In pair correlation functions were deduced. We found a total absence of interlayer pair correlation along [001] and a strong negative correlation for the nearest neighbor (nn) pair along [110], corresponding to a repulsive interaction energy of 0.1 eV far the nn In pairs along [110]. In addition, a weak long-range oscillation in the correlation function along [110] is observed.