Evolution of Ge and SiGe Quantum Dots under Excimer Laser Annealing

We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing. Investigation of the coarsening and relaxation of the dots shows that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer, while the SiGe dots on Si_0.77Ge_0.23 film relax by lattice distortion to coherent dots, which results from the obvious interface between the SiGe dots and the Si_0.77Ge_0.23 film. The results are suggested and sustained by Vanderbilt and Wickham's theory, and also demonstrate that no bulk diffusion occurs during the excimer laser annealing.