Si/Si_1-xGe_x dots grown by selective epitaxy

Using low-pressure chemical vapour deposition, single-layer SiGe and single-quantum-well (SAW) Si/SiGe dots were deposited by selective epitaxy in SiO₂ windows using a SiCl₂H₂/GeH₂/H₂-based chemistry. The uniformity of selective deposition was investigated over a range of pads from 300 mu m down to 0.14 mu m. No change of growth rate and Ge fraction in SiGe was observed for patterns down to 2 mu m. Only for 0.18 mu m wide dots was a slight increase in Si height measured as compared with the unpatterned area. However, the SiGe layer in the saw dots was 5-4 times thicker, which could be dye to islands or to an enhanced growth of SiGe in the small openings. Arrays with hundreds of millions of 0.15 mu m single-quantum-well Si/SiGe dots very uniform in height could be deposited.