Phosphorus-mediated growth of Ge quantum dots on Si(0Â 0Â 1)

The influence of pre-deposited phosphorus atoms on the formation of self-assembled Ge quantum dots (QDs) on Si(0 0 1) is investigated by solid-source molecular beam epitaxy (MBE) and atomic force microscopy (AFM). AFM images show that P atoms have a great influence on the size and density of Ge QDs. In the presence of 0.1 ML P atoms, highly uniform self-assembled Ge QDs with a mean base size of 32 nm and an areal density of 1.4×1011 cm−2 are obtained. These QDs are dome shaped with a size distribution width at half-maximum of 8 nm, which have a higher aspect ratio and are more uniform in size than dots obtained with the presence of C atoms. The strain effect on the nucleation and growth of Ge dots induced by P atoms is discussed. In situ annealing reveals the non-metastable nature of the as-grown uniform dots and they are formed under highly kinetically limited condition.