Slowdown in development of self-assembled lnAs/GaAs(001) dots near the critical thickness

By strain relaxation measurements using reflection high-energy electron diffraction, it is observed that development of the self-assembled InAs/GaAs(001) dots continues after In deposition is stopped just above the critical thickness under As₄ atmosphere. Transmission electron microscope and photoluminescence measurements reveal that dot size increases considerably during this postdeposition process. On the other hand, the dot size increases only slightly during the postdeposition if the amount of In is greater than the critical thickness. Energetics within a finite surface area for a dot shows that the energy barrier for the transformation from the metastable InAs wetting layer to the optimum dot on the thinner wetting layer is high and suppresses the transformation near the critical thickness. Development of the dot density is also illustrated by calculating the nucleation rate from the thickness-dependent barrier height.