Germanium dots with highly uniform size distribution grown on Si(100) substrate by molecular beam epitaxy

The growth of very uniform Ge dots on Si(100) is achieved by using molecular beam epitaxy. The atomic force microscopy and the transmission electron microscopic observations illustrate that the size uniformity of the dots is not worse than $\text{±3\%,}$ i.e., the base dimension is $\text{100±3\hspace{0.17em}}\mathrm{nm}.$ The Raman spectrum reveals a peak downward shift of Ge-Ge mode caused by the phonon confinement in the Ge dots. A very narrow photoluminescence peak with the width of 1.6 meV at the energy of 0.767 eV is observed at the temperature of 16 K. We attribute this peak to the free exciton longitudinal acoustic phonon replica originated from the Ge dots.