Small SiGe quantum dots obtained by excimer laser annealing

In this paper, we obtain SiGe quantum dots with the diameters and density of 15–20 nm and 1.8×1011 cm−2, respectively, by 193 nm excimer laser annealing of Si0.77Ge0.23 strained films. Under the excimer laser annealing, only surface atoms diffusion happens. From the detailed statistical information about the size and shape of the quantum dots with different annealing time, it is shown that the as-grown self-assembled quantum dots, especially the {1 0 5}-faceted dots, are not stable and disappear before the appearance of the laser-induced quantum dots. Based on the calculation of surface energy and surface chemical potential, we show that the {1 0 3}-faceted as-grown self-assembled quantum dots are more heavily strained than the {1 0 5}-faceted ones, and the heavy strain in the dot can decrease the surface energy of the dot facets. The formation of the laser-induced quantum dots, which is also with heavy strain, is attributed to kinetic constraint.