Kinetics of the heteroepitaxial growth of Ge layer at low temperature on Si(001) in UHV-CVD.
The Ge growth at 330 °C by ultrahigh vacuum chemical vapour deposition is investigated in real time by reflection high energy electron diffraction (RHEED) in combination with atomic force microscopy and Rutherford back scattering spectrometry (RBS). The Stranski-Krastanov-related 2D to 3D transition is avoided at low temperature and the major part of the relaxation process occurs during the deposition of the first two monolayers. The very low growth rate observed during this first step is related to the deposition of Ge on Si. Beyond 2 deposited MLs, the growth rate increases drastically due to a complete coverage of Si by Ge. Finally, the deposition of Ge at 330 °C results in an in-plane lattice parameter approaching 90% of that of Ge bulk and a flat surface with rms roughness of 0.6 nm for a film thickness lower than 30 nm.