Island shape instabilities and surfactant-like effects in the growth of InGaAs/GaAs quantum dots

InGaAs/GaAs island formation during vapor phase epitaxy showed diverging behaviors when varying group V partial pressures (PP). Differences include changes in critical thicknesses for the onset of the Stranski-Krastanow (S-K) transformation, surface coverages, ratios between coherent and incoherent islands, and dissimilar morphologies upon annealing. These results show that slightly different values for the 2D-3D transition can also be obtained in InGaAs/GaAs depending on AsH₃ PP. Photoluminescence spectroscopy of capped islands showed that the wetting layer thickness does not change beyond the onset of the S-K transformation for conditions producing stable islands. Annealing experiments done at high AsH₃ PP show Ostwald ripening, but we also observe that small, high density, lens-shaped islands are unaffected by prolonged annealing and do not ripen when an `optimum' low AsH<sub>3</sub> PP is used during the island growth and in-situ annealing. The later experiments show that small lens shaped islands can be found in equilibrium if InGaAs surface energies are minimized. These findings lead to the conclusion that AsH<sub>3</sub> can raise surface energies acting as an impurity-free `morphactant' in InGaAs growth.