We give a thermodynamical interpretation of the size and shape dispersion of $\mathrm{In}\mathrm{As}∕\mathrm{In}\mathrm{P}\left(001\right)$ quantum dots (QD’s) grown by metalorganic vapor phase epitaxy. A careful determination of the QD geometry is performed by analyzing transmission electron microscopy images. QD’s are parallelogram shaped, with edges slightly elongated along the [1-30] and [3-10] directions. The analytical model of Tersoff et al. is adapted to our QD geometry to determine the amount of elastic energy relaxed during the QD formation. A comparison between experiments and calculations shows that QD elongation becomes favorable when the volume of QD’s exceeds a critical value, which is determined experimentally and theoretically with quantitatively good agreement. QD anisotropy is shown to be strongly dependent on the excess of material provided on the growth surface after they have reached their critical volume.

• Received 21 December 2005

DOI:https://doi.org/10.1103/PhysRevB.73.165321